Contact dermatitis is the name for any skin inflammation that occurs when the skin's surface comes in contact with a substance originating outside the body. There are two major categories of contact dermatitis, irritant and allergic. Irritant dermatitis is essentially a direct injury to the skin, caused by such compounds as acids, alkalis, phenol, and detergents. The immune system is not involved in irritant dermatitis, and the person's skin is damaged without prior sensitization.
In allergic dermatitis, however, the patient's skin reacts to a substance to which it has become sensitized. A third type of dermatitis, photo contact dermatitis, is triggered by exposure of the skin to light following the application of certain cosmetics or chemicals. Photo contact dermatitis may be either irritant or allergic.
Contact dermatitis may be either an acute or chronic skin disorder. In general, allergic contact dermatitis is more severe and acute in its onset than irritant contact dermatitis. In irritant contact dermatitis, the rash is usually limited to the area that was exposed to the substance, whereas in allergic contact dermatitis, the rash often spreads beyond the area directly exposed to the allergen. Irritant contact dermatitis most commonly affects the hands, while allergic contact dermatitis may be found on almost any part of the body, including the armpits and genitals. Allergic contact dermatitis is more likely to involve swelling of the skin and the development of small fluid-filled blisters than irritant contact dermatitis.
Photo contact dermatitis is usually limited to the area of skin exposed to direct light. If the substance that was applied to the skin was changed to an irritant by light exposure, the primary symptom is a burning sensation resembling sunburn . If the substance was changed to an allergen, the primary sensation is itching .
Contact dermatitis is a common complaint in people of all ages, in part because of the large number of potential irritants and allergens in the contemporary environment. One textbook on contact dermatitis runs to over 1,100 pages of descriptions of the various manufactured products and other substances that can cause these skin reactions.
In the United States, contact dermatitis ranks among the top 10 reasons for visits to primary care doctors and accounts for 7 percent of all visits to dermatologists. Every year between 10 and 50 million Americans in all age groups develop an allergic rash following contact with poison ivy or poison oak .
About 20 percent of children in the general United States population develop allergic contact dermatitis at some point prior to adolescence . Between 20 percent and 35 percent of healthy children react to one or more allergens on standard patch tests. Children of parents with allergic contact dermatitis have a 60 percent greater chance of having a positive reaction on a patch test themselves.
Contact dermatitis is more likely to affect Caucasians than African, Asian, or Native Americans. People with fair skin and red hair are particularly susceptible to contact dermatitis.
With regard to sex, girls are twice as likely as boys to develop both irritant and allergic skin reactions.
Causes and symptoms
Irritant contact dermatitis
Irritant contact dermatitis (ICD) is the more commonly reported of the two kinds of contact dermatitis, and is seen in about 80 percent of cases. It can be caused by soaps, detergents, solvents, adhesives, fiberglass, and other substances that are able to directly injure the skin by breaking or removing the protective layers of the upper epidermis. Irritants remove lipids, which are fatty substances that help to maintain the integrity of skin cells; irritants also damage the skin's ability to hold water. A common form of irritant contact dermatitis in infants is diaper rash , which develops when the protective epidermal layer of the baby's skin is damaged by long periods of contact with fecal matter and urine.
Most attacks of ICD are slight and confined to the hands and forearms but can affect any part of the body that comes in contact with an irritating substance. The symptoms can take many forms: redness, itching, crusting, swelling, blistering, oozing, dryness, scaling, thickening of the skin, and a feeling of warmth at the site of contact. In extreme cases, severe blistering can occur and open sores can form. Jobs that require frequent skin exposure to water, such as hairdressing and food preparation, can make the skin more susceptible to ICD.
Thin, moist, or already damaged skin is more susceptible to ICD than thick, dry, or intact skin.
Allergic contact dermatitis
Allergic contact dermatitis (ACD) results when repeated exposure to an allergen (an allergy-causing substance) triggers an immune response that inflames the skin. There are two phases in the development of ACD: an induction phase, in which the allergen penetrates the epidermis and is processed by an antigen-presenting cell; and an elicitation phase, in which the sensitized person has a second exposure to the allergen, which produces an inflammatory response several hours or days after the second exposure. Sensitivity to the specific allergen is often lifelong.
Tens of thousands of drugs, pesticides, cosmetics, food additives, commercial chemicals, and other substances have been identified as potential allergens. Fewer than 30, however, are responsible for the majority of ACD cases. Common culprits include poison ivy, poison oak, and poison sumac ; fragrances and preservatives in cosmetics and personal care products, such latex items as gloves and condoms; and formaldehyde. Many people find that they are allergic to the nickel in inexpensive jewelry; some adolescents find that they are allergic to the metal alloys used in orthodontic braces. ACD is usually confined to the area of skin that comes in contact with the allergen. Symptoms range from mild to severe and resemble those of ICD.
Photo contact dermatitis
In photo contact dermatitis, certain substances undergo chemical changes as a result of exposure to light that transform them into either irritants or allergens. Aftershave lotions, sunscreens , and certain topical sulfa drugs may be changed into allergens, while coal tar and certain oils used in manufacturing may become irritants after light exposure.
When to call the doctor
Contact dermatitis is not a medical emergency. It can often be treated at home once the irritant or allergen has been identified. A visit to the doctor may be necessary, however, in order to identify the cause(s) as well as obtain specific recommendations for treatment.
Diagnosis of contact dermatitis begins with a physical examination and asking the patient questions about his or her health and daily activities. When contact dermatitis is suspected, the doctor attempts to learn as much as possible about the child or adolescent's school, sports participation, hobbies, favorite jewelry, use of medications and cosmetics—anything that might shed light on the source of the problem. The doctor will ask when the symptoms started, whether this is the first time they occurred, whether the rash is spreading, whether the primary sensation is itching or burning, and how severe the itching or burning feels.
In some cases, an examination of the home or school may be undertaken; in one interesting case, the doctors discovered that a rash on the back of the child's thighs was an allergic reaction to nickel in the metal parts of the chairs in the child's school. If the dermatitis is mild, responds well to treatment, and does not recur, ordinarily the investigation is at an end. More difficult cases require patch testing to identify the specific allergen.
Two methods of patch testing are used in the early 2000s. The most widely used method, the Finn chamber method, employs a multiwell aluminum patch. Each well is filled with a small amount of the allergen being tested and the patch is taped to normal skin on the patient's upper back. After 48 hours, the patch is removed and an initial reading is taken. A second reading is made a few days later.
The second method of patch testing involves applying a small amount of the test substance to directly to normal skin and covering it with a dressing that keeps air out and keeps the test substance in (occlusive dressing). After 48 hours, the dressing is taken off to see if a reaction has occurred. Identifying the allergen may require repeated testing, can take weeks or months, and is not always successful. Moreover, patch testing works only with ACD, though it is considered an essential step in ruling out ICD.
In a few cases, the doctor may take a skin biopsy in order to rule out certain infectious skin diseases.
The best treatment for contact dermatitis is to identify the allergen or irritating substance and avoid further contact with it. If the culprit is, for instance, a cosmetic, avoidance is a simple matter, but in some situations, avoidance may be impossible or force the sufferer to make drastic changes in his or her life. Barrier creams and such protective clothing as gloves, masks, and long-sleeved shirts are coping devices to reduce the chance of contact dermatitis when avoidance is impossible, though they are not always effective.
For the symptoms themselves, treatments in mild cases include cool compresses and nonprescription lotions and ointments. Diaper rash is often treated by applying various emollient preparations that restore lipids to the child's skin. In older children and adolescents, more severe cases of contact dermatitis are treated with corticosteroids applied to the skin or taken orally. Contact dermatitis that leads to a bacterial skin infection is treated with antibiotics . Although antihistamines do not cure contact dermatitis, the doctor may prescribe them to relieve severe itching.
Herbal remedies have been used for centuries to treat skin disorders including contact dermatitis. An experienced herbalist can recommend the remedies that will be most effective for an individual's condition. Among the herbs often recommended are the following:
- Burdock ( Arctium lappa ) minimizes inflammation and boosts the immune system. It is taken internally as a tea or tincture (a concentrated herbal extract prepared with alcohol).
- Calendula ( Calendula officinalis ) is a natural antiseptic and anti-inflammatory agent. It is applied topically in a lotion, ointment, or oil to the affected area.
- Aloe ( Aloe barbadensis ) gel soothes skin irritations. The gel is applied topically to the affected area.
A homeopath treating a patient with contact dermatitis will do a thorough investigation of the individual's history and exposures before prescribing a remedy. One homeopathic remedy commonly prescribed to relieve the itching associated with contact dermatitis is Rhus toxicodendron , which is taken internally three to four times daily.
Poison ivy, poison oak, and poison sumac are common culprits in cases of allergic contact dermatitis. Within fifteen minutes of exposure to these plants, rash development may be prevented by washing the area with soap and water. The leaves of jewelweed ( Impatiens spp.), which often grows near poison ivy, may neutralize the poison-ivy allergen if rubbed on the skin right after contact. Several topical remedies may help relieve the itching associated with allergic contact dermatitis, including the juice of plantain leaves ( Plantago major ); a paste made of equal parts of green clay and goldenseal root ( Hydrastis canadensis ); a paste made of salt, water, clay, and peppermint ( Mentha piperita ) oil; and calamine lotion.
If the offending substance is promptly identified and avoided, the chances of a rapid and complete recovery are excellent. Otherwise, symptom management—not cure—is the best doctors can offer. Sensitivity to allergens is typically lifelong. For a few people, contact dermatitis becomes a chronic and disabling condition that can have a profound effect on quality of life.
Avoidance or substitution of known or suspected allergens or irritating substances is the best prevention. If avoidance is difficult, barrier creams and protective clothing can be tried. Skin that comes in contact with an offending substance should be thoroughly washed as soon as possible.
Parents should be concerned primarily with identifying the cause(s) of a child or adolescent's contact dermatitis, as treatment is often ineffective until the offending substance can be removed or avoided. Most cases of contact dermatitis are mild and can be treated without disrupting the child's school routine or severely affecting his or her quality of life. In some cases, parents may find it helpful to consult a dermatologist to identify the specific causes and to suggest products that can be substituted for those that are causing the skin reactions.
Antibiotics —Drugs that are designed to kill or inhibit the growth of the bacteria that cause infections.
Corticosteroids —A group of hormones produced naturally by the adrenal gland or manufactured synthetically. They are often used to treat inflammation. Examples include cortisone and prednisone.
Dermatologist —A physician that specializes in diseases and disorders of the skin.
Epidermis —The outermost layer of the human skin.
Immune response —A physiological response of the body controlled by the immune system that involves the production of antibodies to fight off specific foreign substances or agents (antigens).
Lipids —Organic compounds not soluble in water, but soluble in fat solvents such as alcohol. Lipids are stored in the body as energy reserves and are also important components of cell membranes. Commonly known as fats.
Topical —Not ingested; applied to the outside of the body, for example to the skin, eye, or mouth.
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