An Overview of Allergic Contact Dermatitis

Woman by tree scratching arm
IAN HOOTON/SCIENCE PHOTO LIBRARY / Getty Images

In This Article

Table of Contents

Allergic contact dermatitis is a delayed hypersensitivity reaction that involves the interaction of allergens and antibodies, which occurs in phases. The resulting rash is usually very itchy and consists of redness, scaling, fissuring, vesicles, and lichenification.​ Allergic contact dermatitis accounts for 20% of all contact dermatitis reactions.

Symptoms

The symptoms of allergic contact dermatitis include:

  • A raised, red rash
  • Intense itching
  • Blisters, which may ooze fluid
  • Dry, scaly patches
  • Areas of cracked skin
  • Swelling of the skin
  • Hives

The shape and location of the rash are important clues to the cause of the allergen if the pattern of the rash corresponds exactly to the shape of the offending agent such as a watch, metal belt buckle, or waistband.

Symptoms can occur fairly quickly, within a few hours of coming in contact with an offending substance, or they can occur up to several days later. Symptoms may persist for several weeks, even after the offending substance has been removed.

Causes

Allergic contact dermatitis is caused by coming in contact with a substance to which you have an allergy.

Some of the more common substances that trigger allergic contact dermatitis include:

  • Metal, especially nickel and chromium: These metals are found in many costume jewelry pieces, belt buckles, and the snaps in clothing (including the backs of buttons on jeans).
  • Rubber or latex: Found in items like gloves, condoms, balloons, and shoes
  • Fragrance in cosmetic products: This includes fragranced soaps, perfumes, shampoos, and lotions
  • Preservatives used in cosmetic products: Common offenders include parabens, quaternium-15, DMDM hydantoin, formaldehyde, and isothiazolinones
  • Sunscreen products: The active ingredient oxybenzone, found in many sunscreens and sunblocks, is a common cause of photoallergic contact dermatitis
  • Poisonous plants: Poison ivy, poison oak, and poison sumac
  • Adhesives: For example, those used in non-stick bandages and medical adhesive tape, glue used to apply false eyelashes, or tape used to for wigs
  • Topical medications: Triple-antibiotic ointments (like Neosporin) are common triggers. Both topical over-the-counter and prescription medications can trigger reactions.
  • Balsam of Peru: A common ingredient in cosmetics as well as food and drinks

Allergic vs. Irritant Contact Dermatitis

There are two types of contact dermatitis: allergic and irritant. Both types develop because of something the skin as come into contact with. The skin comes in contact with an offending substance.

With irritant contact dermatitis, the skin reacts because of a physical irritation by a substance the skin has come into contact with. The substance has irritated the skin, but it's not a true allergy because there is no immune response.

Allergic contact dermatitis is different. It is a true allergy to a substance. Coming in contact with an offending substance triggers an immune response in the body.

Phases

With allergic contact dermatitis, there are two distinct phases: the sensitization phase and the elicitation phase. The sensitization phase is when the skin first comes in contact with the offending substance. The elicitation phase is when the symptoms appear.

Sensitization Phase

During this phase, an antigen comes in contact with the skin. Because most of the antigens that cause this type of reaction have a low molecular weight, they can easily penetrate the outer layer of the properly functioning epidermis.

The antigen is processed by cells in the basal layer of the epidermis and then presented to white blood cells called T lymphocytes. These T lymphocytes recognize the antigen as foreign and circulate through the bloodstream back to the epidermis.

Elicitation Phase

The elicitation phase occurs in sensitized people who are reexposed to the antigen. The T lymphocytes in the epidermis recognize the antigen as foreign and produce inflammatory chemicals designed to eradicate the antigen.

Unfortunately, these chemicals produce a characteristic rash on the skin.

Diagnosis

Your doctor will examine your rash and, if they suspect contact dermatitis, will ask for a detailed history. Your doctor may ask about your job, your hobbies, and your home life, to help determine which substances may be triggering your rash.

Patch testing is often done to identify allergens. Patch testing is a simple procedure in which small amounts of common allergens are placed on your back with an adhesive sheet.

After 48 hours the patches are removed, and the skin checked for allergic reaction. Another reading of the skin is done approximately two days later.

Patch testing is painless, although you may have some itching or irritation if you have a positive reaction to any of the patches.

Knowing your potential triggers will help you can avoid these substances going forward.

There are many different types of dermatitis, including irritant contact dermatitis and atopic dermatitis (AKA eczema). They all cause a red, irritated, itchy rash. It can be difficult to tell them apart, which is why it's important to see a physician for a definitive diagnosis as treatment differs between them.

Treatment

The mainstay of treatment for allergic contact dermatitis is avoiding the offending allergen if it can be determined.

Over-the-counter hydrocortisone creams can be used if your rash is mild or covers a small area. Apply up to four times per day, or as directed on the product, and rub in gently but completely. Don't use OTC hydrocortisone on babies or young children without first talking to a pediatrician.

Topical steroids may be needed. These will help reduce inflammation and itching. When used as directed, these are very safe and effective treatments.

Oral steroids, such as prednisone, may be prescribed in very severe cases, or where the rash covers large areas of the body.

Other helpful measures to consider, especially if the allergen cannot be identified include:

  • Minimize the topical products you're using. This removes any potential allergens and allows the skin to heal. You may want to use plain water rather than soap and avoid makeup and perfumes altogether.
  • Use ointments instead of creams. Ointments, such as Eucerin or Aquafor, form an occlusive barrier over the skin which can ease discomfort.
  • Avoid botanical extracts found in "fragrance-free" or "natural" products as these can be very allergenic. Also, don't apply any home remedy (e.g., herbal poultices, essential oils, etc.) as these can exacerbate inflammation.
  • Be on the lookout for hidden allergens. For example, earring posts may be made of sterling silver or gold, while the backs are made of nickel.

A Word From Verywell

Allergic contact dermatitis isn't an uncommon problem. It is very itchy and uncomfortable, to the point it affects your daily life (and especially your ability to sleep).

Sometimes it's not clear what has triggered your rash. Because avoiding allergens is key in treating and preventing allergic contact dermatitis, it's important to work with your doctor to identify your particular triggers. Patch testing, plus a bit of detective work, can help in this regard.

Was this page helpful?

Article Sources

  1. Zukiewicz-Sobczak WA, Adamczuk P, Wróblewska P, et al. Allergy to selected cosmetic ingredients. Postepy Dermatol Alergol. 2013 Oct;30(5):307-10. doi:10.5114/pdia.2013.38360


Additional Reading