Contact dermatitis

What it is

Contact dermatitis is a reaction that appears when the skin comes in contact with an irritant or an allergen.⁶ It is a common type of rash.⁸ Irritants and allergies both cause it.⁴

Irritant contact dermatitis happens when a material damages the skin at the point of contact, because the chemical is caustic rather than because of an immune response.¹ Allergic contact dermatitis happens when skin contact with a specific material triggers an immune response, which shows up as a rash.¹ It does not involve IgE, the antibody responsible for classic allergic reactions.⁴ Contact dermatitis can develop right away, or it can occur after months of exposure to a substance.⁴

Citing a 2018 review of studies on contact allergy in the general population, AAFA says contact allergies (contact dermatitis) affect about 20 out of 100 people.⁵ Females are more likely to have contact allergies than males.⁵ People in jobs like health care, hairdressing, painting, metal working and cleaning are more likely to have contact allergies because of their frequent contact with allergens.⁵

Symptoms

ACAAI says symptoms can include a rash, blisters, itching and burning.⁶ AAFA notes that itching and rash are common symptoms.⁴

The most common allergic example is the itchy, red, blistered reaction after touching poison ivy.¹ With a nickel allergy, skin that touches jewelry made with even a very small amount of nickel may become red, bumpy, scaly, itchy or swollen at the point of contact.² These allergic reactions can develop 24 to 48 hours after contact, and once one starts, it may take 14 to 28 days to go away.¹ Once the allergen has been washed off the skin, touching the rash or blisters cannot cause more reactions.¹

The irritant type is often more painful, burning or stinging than itchy, it commonly appears on the hands, and it is frequently due to materials touched at work.¹

Where the rash sits is a clue: with contact dermatitis, you get the rash where you have touched an irritant, such as a chemical, or something you are allergic to, like poison ivy.⁸ ACAAI describes allergic contact dermatitis from chemicals used to make rubber gloves as a different type of skin allergy from latex allergy.⁷ Latex allergy symptoms begin within minutes after exposure to latex-containing products and may include hives, while the rubber glove rash begins 1 to 3 days after wearing the gloves.⁷

What triggers it

AAFA lists the most common triggers of allergic contact dermatitis as metals such as nickel or cobalt; rubber and plastic products, such as those containing latex; plants such as poison ivy, poison oak and poison sumac; preservatives in cosmetics, industrial products and cleaning products; fragrances in perfumes, soaps, lotions and some personal care products; and hair dyes.⁵ Skin contact with cockroach or dust mite matter and certain foods may also cause contact dermatitis.⁵

Nickel is the most common metal that people are allergic to, and more women than men are allergic to it.³ Studies show that body piercing is the single most common cause of nickel allergy.³ Nickel is mixed with other metals to make coins, jewelry, eyeglass frames, home fixtures, keys and other common items, and it can be found in braces, crowns and dentures.³

Rubber (latex) products are among the substances that frequently cause allergic contact dermatitis.¹ ACAAI says chemicals used to make rubber gloves may cause it, recognized by eczema and blisters on the back of the hands.⁷ FDA says allergic reactions to cosmetic products most often appear as itchy, red rashes, a condition known as allergic contact dermatitis, and it names natural rubber, fragrances, preservatives, dyes and metals as the five classes of common cosmetic allergens.¹¹

Poison ivy, poison oak and poison sumac release an oil called urushiol when part of the plant is damaged or burned, and when the oil gets on the skin, most exposed people have an allergic reaction.¹⁰ The reaction can come from touching the plant, or from touching clothing, pets or gardening tools that have touched the oil.² When the plants are burned, airborne sap-coated soot can get into the eyes, nose, throat and respiratory system.⁹

Some allergens cause a skin reaction only when the skin is also exposed to sunlight, a condition called photoallergic contact dermatitis.⁶ It can occur with products such as shaving lotion, sunscreen and some perfumes.⁶

Everyday products can cause it too: soaps, laundry detergents, fabric softeners, shampoos and even excessive exposure to water can cause contact dermatitis.⁶

When to see an allergist

See a health care provider if a rash is bad, if it does not go away, or if other symptoms come with it.⁸ For a rash from poison ivy, oak or sumac, get medical help in severe cases or if the rash is on the face or genitals.¹⁰

To diagnose contact dermatitis, a doctor will do a physical exam and may do allergy testing.⁴ An allergist may do tests, such as a patch test, to identify the allergen causing the rash.¹ In a patch test, a small amount of an allergen is placed on the skin and covered for 48 hours, and a physician inspects the skin after 72 to 96 hours.¹¹ AAAAI says an allergist/immunologist is the best doctor to diagnose nickel allergy.³ For a suspected latex allergy, ACAAI says the best thing to do is see an allergist.⁷

After contact with a poisonous plant, call 911 or go to a hospital emergency room for a severe allergic reaction, like swelling or difficulty breathing.¹⁰ FDA says anaphylaxis is rare with cosmetic products but is a severe allergic reaction that can be life-threatening.¹¹ Its symptoms include a loss of consciousness, shortness of breath, trouble swallowing, lightheadedness, chest pain, a rapid, weak pulse, nausea and vomiting, and if they occur, call 911 and seek medical attention immediately.¹¹

A board-certified allergist can help determine whether symptoms are the result of allergies, so for questions about care, talk to an allergist.⁶