Areas of temporary skin discoloration may
appear and are sometimes due to healed injuries. Scratching open a healing lesion may result in scarring and may enlarge the rash.

Classification

The term eczema refers to a set of clinical characteristics.
Classification of the underlying diseases has been haphazard and
unsystematic, with many synonyms
used to describe the same condition.

A type of eczema may be described
by location (e.g., hand eczema), by specific appearance (eczema craquele
or discoid), or by possible cause (varicose eczema).

Further adding to
the confusion, many sources use the term eczema for the most common type
of eczema (atopic dermatitis) interchangeably.

The European Academy of Allergology and Clinical Immunology (EAACI)
published a position paper in 2001 which simplifies the nomenclature of
allergy-related diseases including atopic and allergic contact eczemas.

Non-allergic eczemas are not affected by this proposal.
The classifications below is ordered by incidence frequency.

Common

• Atopic eczema
  (aka infantile e., flexural e., atopic dermatitis) is an allergic
  disease believed to have a hereditary component and often runs in
  families whose members also have asthma. 
•  Itchy rash is particularly noticeable on head and scalp, neck, inside of elbows, behind knees, and buttocks. Experts are urging doctors to be more vigilant in weeding out cases that are, in actuality, irritant contact dermatitis. It is very common in developed countries, and rising. (L20)
• Contact dermatitis is of two types: allergic (resulting from a delayed reaction to some allergen, such as poison ivy or nickel), and irritant (resulting from direct reaction to a detergent, such as sodium lauryl sulfate,
  for example). Some substances act both as allergen and irritant (wet
  cement, for example). Other substances cause a problem after sunlight
  exposure, bringing on phototoxic dermatitis. About three quarters of
  cases of contact eczema are of the irritant type, which is the most
  common occupational skin disease. Contact eczema is curable, provided
  the offending substance can be avoided and its traces removed from one’s
  environment.
• Xerotic eczema
  (aka asteatotic e., e. craquele or craquelatum, winter itch, pruritus
  hiemalis) is dry skin that becomes so serious it turns into eczema. It
  worsens in dry winter weather, and limbs and trunk are most often
  affected. The itchy, tender skin resembles a dry, cracked, river bed.
  This disorder is very common among the older population. Ichthyosis is a related disorder.
• Seborrhoeic dermatitis or Seborrheic dermatitis (“cradle cap” in infants) is a condition sometimes classified as a form of eczema that is closely related to dandruff.
  It causes dry or greasy peeling of the scalp, eyebrows, and face, and
  sometimes trunk. The condition is harmless except in severe cases of
  cradle cap. In newborns it causes a thick, yellow crusty scalp rash
  called cradle cap, which seems related to lack of biotin and is often curable.

Less common

• Dyshidrosis
  (aka dyshidrotic e., pompholyx, vesicular palmoplantar dermatitis,
  housewife’s eczema) only occurs on palms, soles, and sides of fingers
  and toes. Tiny opaque bumps called vesicles,
  thickening, and cracks are accompanied by itching, which gets worse at
  night. A common type of hand eczema, it worsens in warm weather.
• Discoid eczema (aka nummular e., exudative e., microbial e.) is characterized by round
  spots of oozing or dry rash, with clear boundaries, often on lower
  legs. It is usually worse in winter. Cause is unknown, and the condition
  tends to come and go.
• Venous eczema
  (aka gravitational e., stasis dermatitis, varicose e.) occurs in people
  with impaired circulation, varicose veins and edema, and is
  particularly common in the ankle area of people over 50. There is
  redness, scaling, darkening of the skin and itching. The disorder
  predisposes to leg ulcers.
• Dermatitis herpetiformis
  (aka Duhring’s Disease) causes intensely itchy and typically
  symmetrical rash on arms, thighs, knees, and back. It is directly
  related to celiac disease, can often be put into remission with appropriate diet, and tends to get worse at night.
• Neurodermatitis (aka lichen simplex chronicus, localized scratch dermatitis) is an itchy area of thickened, pigmented eczema patch that results from habitual
  rubbing and scratching. Usually there is only one spot. Often curable
  through behavior modification and anti-inflammatory medication. Prurigo nodularis is a related disorder showing multiple lumps.
• Autoeczematization (aka id reaction, autosensitization) is an eczematous reaction to an
  infection with parasites, fungi, bacteria or viruses. It is completely
  curable with the clearance of the original infection that caused it. The
  appearance varies depending on the cause. It always occurs some
  distance away from the original infection.
• There are also eczemas overlaid by viral infections (e. herpeticum, e. vaccinatum), and eczemas resulting from underlying disease (e.g. lymphoma).
  Eczemas originating from ingestion of medications, foods, and
  chemicals, have not yet been clearly systematized. Other rare eczematous
  disorders exist in addition to those listed here.

Cause

The cause of eczema is unknown but is presumed to be a combination of genetic and environmental factors^.
The hygiene hypothesis postulates that the cause of asthma, eczema, and other allergic diseases is an unusually clean environment. It is supported by epidemiologic studies for asthma.

The hypothesis states that exposure to bacteria and other immune system
modulators is important during development, and missing out on this
exposure increases risk for asthma and allergy.

While it has been suggested that eczema may sometimes be an allergic reaction to the excrement from house dust mites, ^{with up to 5% of people showing antibodies to the mites, the overall role this plays awaits further corroboration.}

Researchers have compared the prevalence of eczema in people who also suffer from celiac
disease to eczema prevalence in control subjects, and have found that
eczema occurs about three times more frequently in celiac disease
patients and about two times more frequently in relatives of celiac
patients, potentially indicating a genetic link between the two conditions.

Diagnosis

Diagnosis of eczema is based mostly on history and physical examination. However, in uncertain cases, skin biopsy may be useful.

Prevention

Those with eczema should not get the smallpox vaccination due to risk of developing eczema vaccinatum, a potentially severe and sometimes fatal complication.

Treatment

There is no known cure for eczema; therefore, treatments aim to
control the symptoms by reducing inflammation and relieving itching.

Medications

Corticosteroids

Corticosteroids are highly effective in controlling or suppressing symptoms in most cases. ^{For mild-moderate eczema a weak steroid may be used, while in more severe cases a higher-potency steroid
may be used. In severe cases, oral or injectable corticosteroids may be
used. While these usually bring about rapid improvements, they have
greater side effects.}

Side effects

Prolonged use of topical corticosteroids is thought to increase the
risk of side effects, the most common of which is the skin becoming thin
and fragile.
^{Because of this, if used on the face or other delicate skin, only a
low-strength steroid should be used.}

Additionally, high-strength
steroids used over large areas, or under occlusion, may be significantly absorbed into the body, causing hypothalamic-pituitary-adrenal axis suppression.

Finally by their immunosuppressive action they can, if used without antibiotics or antifungal drugs, lead to some skin infections (fungal or bacterial).

Care must be taken to avoid the eyes, as topical corticosteroids applied to the eye can cause ^{or cataracts.}

Because of the risks associated with this type of drug, a steroid of
an appropriate strength should be sparingly applied only to control an
episode of eczema. Once the desired response has been achieved, it
should be discontinued and replaced with emollients
as maintenance therapy.

Corticosteroids are generally considered safe
to use in the short- to medium-term for controlling eczema, with no
significant side effects differing from treatment with non-steroidal
ointment.

Some recent research claims that topically applied corticosteroids
did not significantly increase the risk of skin thinning, stretch marks
or HPA axis suppression (and where such suppression did occur, it was
mild and reversible where the corticosteroids were used for limited
periods of time).

Further, skin conditions are often under-treated
because of fears of side effects. This has led some researchers to
suggest that the usual dosage instructions should be changed from “Use
sparingly” to “Apply enough to cover affected areas”, and that specific
dosage directions using “fingertip units” or FTUs be provided, along
with photos to illustrate FTUs.

However, caution must always be used as long-term use, prolonged
widespread coverage, or use with occlusion, can create side effects that
are permanent and resistant to treatment.

Topical immunosuppressants

Topical immunosuppressants like pimecrolimus and tacrolimus were developed after topical corticosteroids
had come into widespread use. These newer agents effectively suppress
the immune system in the affected area, and appear to yield better
results in some populations.

The U.S. Food and Drug Administration has issued a public health advisory about the possible risk of lymph node or skin cancer from use of these products, ^{but many professional medical organizations disagree with the FDA’s findings;}

• The postulation is that the immune system may help remove some
  pre-cancerous abnormal cells which is prevented by these drugs. However,
  any chronic inflammatory condition such as eczema, by the very nature
  of increased metabolism and cell replication, has a tiny associated risk
  of cancer.
• Current practice by UK dermatologists is not to consider this a
  significant real concern and they are increasingly recommending the use
  of these new drugs.
  ^{The dramatic improvement on the condition can significantly improve the
  quality of life of sufferers (and families kept awake by the distress
  of affected children). The major debate, in the UK, has been about the
  cost of such newer treatments and, given only finite NHS resources, when they are most appropriate to use.}
• In addition to cancer risk, there are other potential side effects
  with this class of drugs. Adverse reactions including severe flushing,
  headaches, flu-like syndrome, photosensitive reactivity and possible
  drug interactions with a variety of medications, alcohol and grapefruit.

Systemic immunosuppressants

When eczema is severe and does not respond to other forms of treatment, immunosuppressant
drugs are sometimes prescribed. These dampen the immune system and can
result in dramatic improvements to the patient’s eczema.

However,
immunosuppressants can cause side effects on the body. As such, patients
must undergo regular blood tests and be closely monitored by a doctor.
In the UK, the most commonly used immunosuppressants for eczema are ciclosporin, azathioprine and methotrexate. These drugs were generally designed for other medical conditions but have been found to be effective against eczema.

Itch relief

Anti-itch drugs, often antihistamine,
and dermasil may reduce the itch during a flare up of eczema, and the
reduced scratching in turn reduces damage and irritation to the skin
(the “itch cycle”).
However, in some cases, significant benefit may be due to the sedative
side effects of these drugs, rather than their specific antihistamine
effect.

Thus sedating antihistamines such as promethazine (Phenergan) or
diphenhydramine (Benadryl) may be more effective at preventing night
time scratching than the newer, nonsedating antihistamines.^[26]
Capsaicin applied to the skin acts as a counter irritant.

Hydrocortisone applied to the skin aids in temporary itch relief. Temporary yet significant and fast-acting relief can be found by
cooling the skin via water (swimming, cool water bath or wet washcloth),
air (direct output of an air conditioning vent), or careful use of an ice pack (wrapped in soft smooth cloth, e.g., pillow case, to protect skin from damage).

Moisturizers

Eczema can be exacerbated by dryness
of the skin. Moisturizing is one of the most important self-care
treatments for eczema. Keeping the affected area moistened can promote
skin healing and relief of symptoms. Soaps and detergents should not be used on affected skin because they can strip natural skin oils and lead to excessive dryness.

Moistening agents are called emollients.
In general, it is best to match thicker ointments to the driest,
flakiest skin. Light emollients may not have any effect on severely dry
skin.

Moisturizing gloves (gloves which keep emollients in contact with
skin on the hands) can be worn while sleeping.

Generally, twice-daily
applications of emollients work best. Ointments,
with less water content, stay on the skin longer and need fewer
applications, but they can be greasy and inconvenient. Steroids may also
be mixed in with ointments.

For unbroken skin, direct application of waterproof tape with or
without an emollient or prescription ointment can improve moisture
levels and skin integrity which allows the skin to heal.

This treatment
regimen can also help prevent the skin from cracking, as well as put a
stop to the itch cycle. The end result is reduced lichenification (the
roughening of skin from repeated scratching).

Taping works best on skin
away from joints. There is a disagreement whether baths are desirable or a necessary evil. For example, the Mayo Clinic advises against daily baths to avoid skin drying. ^{On the other hand, the American Academy of Dermatology
claims “it is a common misconception that bathing dries the skin and
should be kept to a bare minimum” and recommends bathing to hydrate
skin. They even suggest up to 3 short baths a day for people with severe
eczema.}

According to them, a moisturizer should be applied within 3
minutes to trap the moisture from bath in the skin.

Anecdotal evidence suggested that soft water could have therapeutic effects for people with eczema currently using hard water.
^{However, a trial involving 336 children with eczema showed no objective
difference in outcomes between the children whose homes were fitted
with a water softener and those without.}

Ceramides, which are the major lipid constituent of the stratum corneum, have been used in the treatment of eczema.
They are often one of the ingredients of modern moisturizers. These
lipids were also successfully produced synthetically in the laboratory.^[34]

However, detergents are so ubiquitous in modern environments in items
like tissues, and so persistent on surfaces, “safe” soaps are necessary
to remove them from the skin in order to control eczema.

Although most
eczema recommendations use the terms “detergents” and “soaps”
interchangeably, and tell eczema sufferers to avoid both, detergents and soaps
are not the same and are not equally problematic to eczema sufferers.

Detergents, which differ from soap in that they commonly have a sulfate
polar group, increase the permeability of skin membranes in a way that
soaps and water alone do not.

Sodium lauryl sulfate,
the most common household detergent, has been shown to amplify the
allergenicity of other substances (“increase antigen penetration”).

Light therapy using ultraviolet light can help control eczema.
^{UVA is mostly used, but UVB and Narrow Band UVB are also used.
Overexposure to ultraviolet light carries its own risks, particularly
potential skin cancer from exposure.}

When light therapy alone is found to be ineffective, the treatment is
performed with the application (or ingestion) of a substance called psoralen. This PUVA
(Psoralen + UVA) combination therapy is termed photo-chemotherapy.

Psoralens make the skin more sensitive to UV light, thus allowing lower
doses of UVA to be used. However, the increased sensitivity to UV light
also puts the patient at greater risk for skin cancer.

Diet

Recent studies provide hints that food allergy
may trigger atopic dermatitis. For these people, identifying the
allergens could lead to an avoidance diet to help minimize symptoms,
although this approach is still in an experimental stage.

Dietary elements that have been reported to trigger eczema include dairy products, coffee (both caffeinated and decaffeinated), soybean products, eggs, nuts, wheat and maize (sweet corn), though food allergies may vary from person to person.

However, in 2009, researchers at National Jewish Medical and Research Center found that eczema patients were especially prone to misdiagnosis of food allergies.

A study led by researchers at the University of California, San Diego School of Medicine suggests that use of oral vitamin D3
supplements bolsters production of a protective chemical normally found
in the skin, and may help prevent skin infections that are a common
result of atopic dermatitis, the most common form of eczema.

It can be noted that the production of vitamin D3 is catalyzed by UV radiation and may influence histocompatibility expression, correlating with both the seasonality of eczema and its relation to the immune system.

Alternative therapies

A number of alternative therapies are used for eczema including:

• Sulfur
  has been used for many years as a topical treatment in the alleviation
  of eczema, although this could be suppressive. It was fashionable in the
  Victorian and Edwardian eras. However, there is currently no scientific
  evidence for the claim that sulfur treatment relieves eczema.
• Probiotics are live microorganisms taken orally, such as the Lactobacillus bacteria found in yogurt.
  They are not effective for treating eczema in older populations, but
  some research points to some strains of beneficial microorganisms having
  the ability to prevent the triad of allergies, eczema and asthma,
  although in rare cases some species of probiotic bacteria have a very
  small risk of infection in those with poor immune system response.
• Traditional Chinese medicine: According to American Academy of Dermatology,
  while certain blends of Chinese herbal medicines have been proven
  effective in controlling eczema, they have also proven toxic with severe
  consequences.
  ^{In Chinese Medicine diagnosis, eczema is often considered a
  manifestation of underlying ill health. Treatment aims to improve the
  overall health of the individual, therefore not only resolving the
  eczema but improving quality of life (energy level, digestion, disease
  resistance, etc.).
  A recent study published in the British Journal of Dermatology
  describes improvements in quality of life and reduced need for topical
  corticosteroid application.
  Another British trial with ten different plants traditionally used in
  Chinese medicine for eczema treatment suggest a benefit with herbal
  remedy, but reviewers noted that the blinding was not maintained, leaving the results invalid.}
• Other remedies lacking scientific evidence include chiropractic spinal manipulation and acupuncture.

Patients can also wear clothing designed specifically to manage the itching, scratching and peeling associated with eczema.

Behavioural approach

In the 1980s, Swedish dermatologist
Peter Noren developed a behavioural approach to the treatment of long
term atopic eczema.

This approach has been further developed by
dermatologist Richard Staughton and psychiatrist Christopher Bridgett at the Chelsea and Westminster Hospital in London.

Patients undergo a six-week monitored program involving scratch habit
reversal and self-awareness of scratching levels.

For long-term eczema
sufferers, scratching can become habitual. Sometimes scratching becomes a
reflex, resulting in scratching without conscious awareness, rather
than from the feeling of itchiness itself.

The habit reversal program is
done in conjunction with the standard applied emollient/corticosteroid
treatments so that the skin can heal. It also reduces future scratching,
as well as reduces the likelihood of further flareups. The behavioural
approach can give an eczema sufferer some control over the degree of
severity of eczema.

Epidemiology

Globally eczema affected approximately 230 million people as of 2010 (3.5% of the population).

The lifetime clinician-recorded prevalence of eczema has been seen to
peak in infancy, with female predominance of eczema presentations
occurring during the reproductive period of 15–49 years.

Although little data on the trend of eczema prevalence over time exists
prior to the Second World War (1939–45), the prevalence of eczema has
been found to have increased substantially in the latter half of the
20th Century, with eczema in school-aged children being found to
increase between the late 1940s and 2000.

A review of epidemiological data in the UK has also found an inexorable rise in the prevalence of eczema over time.
Further recent increases in the incidence and lifetime prevalence of
eczema in England have also been reported, such that an estimated
5,773,700 or about one in every nine people have been diagnosed with the
disease by a clinician at some point in their lives.

Research

Other than direct treatments of the symptoms, no cure is presently
known for most types of dermatitis; even cortisone treatments and
immunomodulation may often have only minor effects on what may be a
complex problem. Even though the effects of eczema are no longer active
the person diagnosed is still subject to relapse.

The condition is often
related to family history of allergies. Damage from the enzymatic activity of allergens is usually prevented by the body’s own protease inhibitors, such as, LEKTI, produced from the gene SPINK5. Mutations in this gene are known to cause Netherton’s syndrome, which is a congenital erythroderma.

These patients nearly always develop atopic disease, including hay
fever, food allergy, urticaria and asthma. Such evidence supports the
hypothesis that skin damage from allergens may be the cause of eczema,
and may provide a venue for further treatment.

Another study identified a gene that the researchers believe to be
the cause of inherited eczema and some related disorders. The gene
produces the protein filaggrin, the lack of which causes dry skin and impaired skin barrier function.

A recent study indicated that two specific chemicals found in the
blood are connected to the itching sensations associated with eczema.
The chemicals are Brain-derived neurotrophic factor (BDNF) and Substance P.

In a genome-wide study published on Dec 25, 2011 in Nature Genetics, researchers reported discovery of three new genetic variants associated with eczema. They are OVOL1, ACTL9 and IL4-KIF3A.

Eczema has increased dramatically in England
as a study showed a 42% rise in diagnosis of the condition between 2001
and 2005, by which time it was estimated to affect 5.7 million adults
and children. A paper in the Journal of the Royal Society of Medicine says Eczema is thought to be a trigger for other allergic conditions. GP records show over 9 million patients were used by researchers to assess how many people have the skin disorder.