Contact dermatitis usually occurs on areas of your body that have been directly exposed to the substance — for example, along a calf that brushed against poison ivy or under a watchband that triggers an allergy. The reaction usually develops within minutes to hours of exposure to an irritating substance or allergen. The rash can last two to four weeks.
Signs and symptoms of contact dermatitis include:
- Red rash or bumps
- Itching, which may be severe
- Dry, cracked, scaly skin, if your condition is chronic
- Blisters, draining fluid and crusting, if your reaction is severe
- Swelling, burning or tenderness
The severity of the rash depends on:
- How long you're exposed
- The strength of the substance that caused the rash
- Environmental factors, such as temperature, airflow and sweating from wearing gloves
- Your genetic makeup, which can affect how you respond to certain substances
When to see a doctor
See your doctor if:
- The rash is so uncomfortable that you are losing sleep or are distracted from your daily routine
- The rash is painful, severe or widespread
- You're embarrassed by the way your skin looks
- The rash doesn't get better within a few weeks
- The rash affects your face or genitals
Seek immediate medical care in the following situations:
- You think your skin is infected — clues include fever and pus oozing from blisters.
- Your lungs, eyes or nasal passages are painful and inflamed, perhaps from inhaling an allergen.
- You think the rash has damaged the mucous lining of your mouth and digestive tract.
Contact dermatitis is caused by a substance you're exposed to that irritates your skin or triggers an allergic reaction. The substance could be one of thousands of known allergens and irritants. Some of these substances may cause both irritant contact dermatitis and allergic contact dermatitis.
Irritant contact dermatitis is the most common type. This nonallergic inflammatory reaction occurs when a substance damages your skin's outer protective layer.
Some people react to strong irritants after a single exposure. Others may develop signs and symptoms after repeated exposures to even mild irritants. And some people develop a tolerance to the substance over time.
Common irritants include:
- Rubbing alcohol
- Personal care products, such as soaps, deodorants and cosmetics
- Airborne substances, such as sawdust or wool dust
- Burdock, a plant used in alternative medicine therapies
Allergic contact dermatitis occurs when a substance to which you're sensitive (allergen) triggers an immune reaction in your skin. It usually affects only the area that came into contact with the allergen. But it may be triggered by something that enters your body through foods, flavorings, medicine, or medical or dental procedures (systemic contact dermatitis).
You may become sensitized to a strong allergen such as poison ivy after a single exposure. Weaker allergens may require multiple exposures over several years to trigger an allergy. Once you develop an allergy to a substance, even a small amount of it can cause a reaction.
Common allergens include:
- Nickel, which is used in jewelry, buckles and many other items
- Medications, such as antibiotic creams and oral antihistamines
- Balsam of Peru, which is used in many products, such as perfumes, cosmetics, mouth rinses and flavorings
- Formaldehyde, which is in adhesives, solvents and other things
- Personal care products, such as deodorants, body washes, hair dyes, cosmetics, nail polish, and herbal preparations for the skin containing eucalyptus, camphor or rosemary
- Skin tattooing and black henna
- Plants such as poison ivy and mango, which contain a highly allergenic substance called urushiol
- Airborne substances, such as from aromatherapy and spray insecticides
- Products that cause a reaction when you're in the sun (photoallergic contact dermatitis), such as some sunscreens and oral medications
The rate of allergic contact dermatitis in children is similar to that in adults. Children develop the condition from the usual offenders and also from exposure to car seats, the plastic in toilet seats and infant clothing snaps.
Occupational contact dermatitis refers to rashes resulting from exposure to allergens or irritants on the job. Certain occupations and hobbies put you at higher risk of this type of contact dermatitis. Examples include:
- Health care workers and pharmaceutical industry employees
- Construction workers
- Hairdressers and cosmetologists
- Scuba divers or swimmers, due to the rubber in face masks or goggles
- Gardeners and agricultural workers
- Chefs and others who work with food
Contact dermatitis can lead to the following complications:
- Chronic itchy, scaly skin. A skin condition called neurodermatitis (lichen simplex chronicus) starts with a patch of itchy skin. You scratch the area, which makes it even itchier. So you keep scratching. Eventually, you may scratch simply out of habit. This condition can cause the affected skin to become discolored, thick and leathery.
- Infection. If you repeatedly scratch a rash, you may cause it to become wet and oozing. This creates a good place for bacteria or fungi to grow and may cause an infection.
General prevention steps include the following:
- Avoid irritants and allergens. Try to identify and avoid substances that irritate your skin or cause an allergic reaction.
- Wash your skin. You might be able to remove most of the rash-causing substance if you wash your skin right away after contacting it. Use a mild, fragrance-free soap and rinse completely. Also wash any clothing or other items that may have come into contact with a plant allergen such as poison ivy.
- Wear protective clothing or gloves. Face masks, goggles, gloves and other protective items can shield you from irritating substances, including household cleansers.
- Apply an iron-on patch to cover metal fasteners next to your skin. This can help you avoid a reaction to jean snaps, for example.
- Apply a barrier cream or gel. These products can provide a protective layer for your skin. For example, an over-the-counter skin cream containing bentoquatam (IvyBlock) may prevent or lessen your skin's reaction to poison ivy.
- Use moisturizer. This can help restore your skin's outermost layer and keep your skin supple.
- Take care around pets. Pets can easily spread to people allergens from plants such as poison ivy.