Contact dermatitis is any inflammation that occurs when the skin’s surface comes directly into contact with an allergen (substances that trigger an exaggerated immune system response) or irritant. Though uncomfortable, the condition is usually not serious, although it should not be left untreated. According to the U.S. Centers for Disease Control and Prevention (CDC), contact dermatitis and eczema are responsible for over 7 million healthcare provider visits every year.

There are two types of contact dermatitis:

• Irritant contact dermatitis (ICD). Caused by a chemical or substance that is naturally irritating to the human skin (e.g., cosmetics, detergents, soaps, food, medication, metals, plants). The most common form of contact dermatitis, it usually resembles a burn.
  
  
• Allergic contact dermatitis (ACD). Caused by an allergic reaction. The reaction varies from a mild irritation to redness and open sores.

Symptoms of contact dermatitis include a red, raised rash on the skin that often itches. Diagnosis of the condition is based the skin’s appearance and the patient’s history of exposure to allergens or irritants.

In a majority of cases, treatment of this condition involves identifying and avoiding allergen triggers that cause contact dermatitis. Effective self-care treatment remedies include:

• Calamine lotion and cool oatmeal baths to relieve itching
• Cold compresses
• Washing with cool, soapy water immediately after exposure
• Moisturizers to help restore the skin’s normal texture

If contact dermatitis occurs frequently, an allergy specialist should be seen to help identify the underlying cause or rule out allergies. The physician may prescribe antihistamines and corticosteroid medications to treat any inflammation.

Contact dermatitis is a localized rash or skin inflammation caused by direct contact with a substance. Contact dermatitis falls into two broad categories, allergic contact dermatitis (ACD) and the more common irritant contact dermatitis (ICD). Apart from the differences in origin, ACD and ICD are often clinically indistinguishable.

People who suffer from contact dermatitis may not experience symptoms the first time they are exposed to a substance. However, as they use or are exposed to the substance repeatedly, the skin becomes sensitized to it over time. Examples of such sensitization may include:

• Use of nail polish remover
• Preservatives in contact lens solutions
• Repeated contact with metals in earring posts or the metal backs of watches

Though the two main categories of contact dermatitis resemble each other in morphology (appearance and cell structure) and the resulting rashes are very similar, they differ in origin. ICD is caused by exposure to a naturally irritating substance to human skin. ACD is caused by a normally harmless substance, which triggers an exaggerated immune system reaction.

In addition, outbreaks of contact dermatitis are more likely to affect certain populations than others. For example, hospital workers who use latex gloves are more likely to suffer from latex-based contact dermatitis, and women are more likely to experience facial contact dermatitis than men because they use facial cosmetics more frequently.

There are two major types of contact dermatitis: irritant contact dermatitis (ICD) and allergic contact dermatitis (ACD).

ICD makes up approximately 80 percent of the cases of contact dermatitis, according to the American Academy of Allergies, Asthma and Immunology. ICD is triggered by exposure to a chemical that is naturally irritating to the human skin. Hands are the most commonly affected body area.

There are several forms of ICD:

• Acute corrosion. Caused by a single exposure to strong acids and alkalis.
  
  
• Acute irritation. Caused by a single exposure to chemicals such as strong solvents and noncorrosive acids and bases.
  
  
• Cumulative irritation. The most common form of ICD, it involves repeated exposures to substances, particularly surfactants (promote lathering) and emulsifiers (skin softener). May be difficult to distinguish from ACD.
  
  
• Phototoxicity. Caused by contact with irritating chemicals that only react when exposed to sunlight. Such substances include shaving lotions, sunscreens, sulfa ointments, some perfumes, coal tar products and oil from the skin of a lime. Symptoms usually affect those areas most susceptible to sunlight, such as the face, arms and upper chest area.

ICD may affect people who are continuously exposed to a certain substance. However, some people have skin that is more sensitive than others to the chemicals that cause ICD. Factors that determine an individual’s susceptibility to ICD include age, genetics, the environment, underlying skin diseases and exposure to other chemicals. Irritant ICD is also more likely in people with dry skin and light-colored (or “fair”) skin. People with a history of atopic dermatitis are more susceptible to ICD.

The most common form of ICD in children is diaper rash, which is a skin reaction to prolonged contact with natural chemicals found in the urine and stool. ICD also can be an occupational illness in adults who are exposed to strong soaps and solvents, such as domestic workers, janitors or hairdressers. Florists, food preparers, constructions workers and health care providers are also at risk for contracting work–related contact dermatitis. Anyone whose household chores or hobbies involve irritating chemicals may also experience ICD.

Mild cases of ICD produce reddening of the skin, but more severe cases may cause swelling or ulceration and resemble a burn. Unlike ACD, symptoms begin immediately after exposure to the harmful substance, or upon repeated exposure to it in the case of cumulative irritation.

ACD involves an immune system reaction that takes place when the skin is exposed to a substance the body perceives as dangerous. To date, more than 3,000 allergens have been identified that are known to cause this condition. ACD may not develop immediately, but instead often appears within 24 to 48 hours after contact with an allergen, or longer in some cases. Specific skin sensitivities vary from person to person, but ACD is a delayed form of hypersensitivity (excessive sensitivity) that generally takes time for the body’s immune defenses to react. ACD can develop at any age. However, adults develop the condition more often than young children or the elderly.

Contact dermatitis caused by an allergic reaction produces localized skin redness (erythema), blistering and severe itching (pruritus). The characteristics of the allergic reaction vary depending on its cause. For example, metal jewelry allergies usually produce rings of inflammation around the body area where the jewelry is worn (e.g., around the neck for a necklace or wrist for a bracelet). Poison ivy produces a pattern of tiny lines in the places where the plant leaves have contacted the skin.

Unlike most allergic reactions, the trigger in ACD is external rather than internal. The skin reacts to external physical contact with an allergen. The initial exposure to the allergen does not cause a rash. Instead, it sensitizes the skin. Once sensitized to an allergen, the body will continue to produce the symptoms of contact dermatitis with each subsequent exposure to the substance. Sensitization can occur after only one exposure to a substance, or after many exposures. In fact, a person can develop ACD after years of being exposed to a substance without a problem.

The presence of preexisting ICD can lead to the development of ACD. Cuts and other common wounds can also contribute by providing an entry point for allergens.

Overtreatment dermatitis is a form of contact dermatitis that occurs when treatment for a separate skin disorder causes ICD.

A history of allergies or atopic dermatitis (eczema) increases the likelihood of allergic contact dermatitis (ACD). Irritant contact dermatitis (ICD) is not caused by allergies. However, many of the irritants that cause ICD can be allergens (substances that trigger an exaggerated immune system response) that trigger ACD in sensitive people.

Some of the irritants that are responsible for causing contact dermatitis are common items many people use regularly. For example, nickel, a common irritant, can easily come into contact with the skin through metal jewelry, zippers, buckles and buttons. Cosmetics – particularly hair dyes – may contain a substance known as paraphenylenediamine (PPD) that causes contact dermatitis in many people. Perfumes often contain preservatives or fragrances that irritate the skin. Poison ivy, oak and sumac are common irritants often encountered outdoors. When touched, the oil in these plants often causes itchy bumps to form on the skin.

Other common irritants and allergens related to contact dermatitis include:

• Adhesives
• Contact lens solutions containing mercury
• Deodorant
• Detergents and soaps
• Drool
• Fabrics and clothing
• Fiberglass
• Food additives
• Foods, particularly those high in nickel, such as fish
• Fruit, especially its peels
• Hair straighteners
• Insecticide
• Jewelry containing cobalt, nickel and other metals
• Latex found in gloves, rubber clothing and condoms
• Leather shoes treated with potassium dichromate
• Medications, particularly topical antibiotics or anesthetics
• Nail polish and nail polish remover
• Pesticides
• Preservatives (e.g., formaldehyde)
• Ragweed pollen
• Rubber
• Solvents
• Sunscreens that contain fragrances and preservatives

The symptoms of the two major forms of contact dermatitis differ slightly. Though irritant contact dermatitis (ICD) symptoms might be more spread out on the skin, allergic contact dermatitis (ACD) symptoms tend to be confined to the area where the offending allergen (substance that triggers an exaggerated immune system response) touched the skin. In addition, a rash caused by ICD may appear immediately whereas ACD’s red rash may not appear until one to three days after exposure.

ICD is more likely to be painful or burning than itchy. Conversely, ACD tends to be very itchy. ICD often affects the hands, which have been directly exposed to the irritant (for example, immersing hands into a sink or pail of offending chemicals or soaps), especially the area between the fingers. It also can affect the face, particularly the eyelids. This type of dermatitis can take as long as a month to completely be resolved.

If the rash does not improve or continues to spread after a few days, patients are advised to see their physician. In the case of severe itching, patients are advised to go to the hospital emergency room. Severe itching could be an indication of a more serious condition.

Symptoms of both forms of contact dermatitis include:

• Blistering (if severe, open sores can form)
• Crusting
• Dryness
• Feeling of warmth at the contact site
• Itching
• Oozing fluid from contact site
• Redness
• Scaliness
• Skin thickening
• Swelling
• Tenderness of the skin in affected areas

To diagnose contact dermatitis, a physician will perform a complete physical examination and compile a thorough medical history. Special attention will be paid to the patient’s history of exposure to an allergen (substance that triggers an exaggerated immune system response) or irritant and the appearance of the skin. Patients are questioned about their daily activities, health, hobbies, workplace responsibilities and use of medications and cosmetics.

The appearance of the rash on the body aids in diagnosing contact dermatitis. Contact dermatitis eruptions often have clear-cut margins, geometric outlines and acute angles that appear anywhere from a few minutes to a few days after contact. Because allergic contact dermatitis (ACD) and irritant contact dermatitis (ICD) skin rashes start out looking the same, it is not always easy to determine whether an allergen or an irritant is the cause of contact dermatitis. If the itchy rash and redness give way to blisters that form a crust or ooze, the condition is more likely to be diagnosed as allergic dermatitis, such as from poison ivy.

The location of the rash may also help the physician pinpoint the substance causing the dermatitis. For instance, contact dermatitis on the neck may be caused by perfume or cologne.

If a case of contact dermatitis is mild and responds well to any initial treatments, testing may not be necessary. However, more severe cases require laboratory testing to identify the responsible substance. Two tests used to diagnose the condition include:

• Patch testing. Allergy testing that introduces a suspect allergen to the skin to determine if an allergic reaction occurs. It often is performed on patients who have chronic, recurring contact dermatitis.
  
  
• Skin lesion biopsy or culture. Examines a sample of skin taken from the site of irritation. Although this test does not reveal the actual allergen, it aids diagnosis by helping to rule out conditions that look similar to contact dermatitis (e.g., psoriasis, fungal infections).

A physician can use a specialized test, known as a photopatch test, to diagnose photocontact dermatitis.

The most effective treatment for contact dermatitis is the avoidance of known allergens (substances that trigger an exaggerated immune system response) or irritating substances. To do this effectively, an individual must first understand what is causing the skin reaction. Though contact dermatitis is often not serious, a physician can help determine its underlying cause.

To help prevent work-related allergic contact dermatitis (ACD) and irritant contact dermatitis (ICD), the National Institute of Occupational Safety and Health (NIOSH) is conducting research to develop specific types of protective clothing, equipment and barrier creams (provide a protective layer from irritants) that can be used on the job. Protective gloves in the workplace as well at home should be worn if contact with known allergens is likely or unavoidable. However, latex gloves are a common cause of contact dermatitis and should be avoided. Vinyl gloves are a better choice. Cotton gloves worn over topical medications and moisturizers are also very helpful.

Work-related situations involving an allergy to a chemical for which no substitute can be found may be better tolerated by using barrier creams and wearing protective clothing. However, airborne allergens may be difficult to avoid.

Other preventative measures involve the use of emollients (substances that soothe the skin) that can be applied three or four times a day to keep the skin moist and prevent itching. Emollients should be applied to slightly wet skin in order to seal in the moisture. In the case of diaper rash, the baby’s diaper should be frequently changed and a protective coat of ointment applied.

There are several types of effective, self-care measures that can be used for the treatment of contact dermatitis symptoms. However, a person with contact dermatitis symptoms should first obtain the advice of a physician before using any self-care treatments. Treatments include:

• Applying calamine lotion to relieve itching.
  
  
• Taking cool oatmeal baths to soothe the skin. It should be noted, however, that oatmeal can be an allergen and actually make the rash worse.
  
  
• Applying cold compresses directly to the blisters.
  
  
• Applying hydrocortisone creams (nonprescription) directly to the skin.
  
  
• Applying moisturizers to help restore the normal texture of the skin. Moisturizers containing nut oils should be avoided because they can exacerbate the reaction.
  
  
• Washing with cool, soapy water immediately after exposure to neutralize and remove the offending substance.

Patients should also wash clothing or any other object that may have come into contact with the offending substance. This will help prevent reexposure. In addition, the affected area should be protected from sunlight until the dermatitis has subsided.

Prescription antihistamines may be used if over-the-counter antihistamines do not relieve the itching. Topical prescription corticosteroid medications may be used to treat an inflammation in a confined area.

Topical corticosteroid medications may lessen the inflammation but should be carefully used, as topical steroids can cause thin skin or rosacea. If the rash covers a large portion of the skin or is severe, a physician may prescribe corticosteroid pills or injections. These are usually tapered gradually over a two-week period to prevent the recurrence of the rash.

Patients with chronic (recurrent) ACD that is not controllable with medications or avoidance may be treated with PUVA phototherapy. Severe skin conditions may respond well to this treatment. However, avoidance of the allergen is the most important treatment.

If contact dermatitis occurs frequently and the cause can not be determined, a physician may recommend an allergy specialist to help identify the trigger. A rash can become chronic if the underlying condition is not effectively treated.

Antibiotics may also be required if a secondary bacterial infection develops at the site of the rash.

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions related to contact dermatitis:

1. Do my symptoms suggest contact dermatitis?
   
   
2. How will you determine if I have contact dermatitis?
   
   
3. What form of contact dermatitis do I have?
   
   
4. Does contact dermatitis pose any danger to my overall health?
   
   
5. What treatment methods are available to me? How effective are they?
   
   
6. When can I expect my symptoms to subside?
   
   
7. Can I spread the rash to other parts of my body or to other people?
   
   
8. What may have caused my contact dermatitis?
   
   
9. Am I likely to develop contact dermatitis again in the future?
   
   
10. How can I prevent contact dermatitis?