Contact Dermatitis

What Is It, Causes, Signs, Symptoms, and More

Author:Lily Guo

Editors:Alyssa Haag,Emily Miao, PharmD,Kelsey LaFayette, DNP, RN, FNP-C

Illustrator:Jessica Reynolds, MS

Copyeditor:Stacy Johnson, LMSW

What is contact dermatitis?

Contact dermatitis is an inflammatory skin condition that occurs after exposure to an allergen or irritant. Specifically, allergic contact dermatitis is caused by a foreign substance coming into contact with the skin, which can lead to skin changes after reexposure to the substance. On the other hand, irritant contact dermatitis is caused by the non–immune-modulated skin irritation from repeated exposure to a substance.

Contact dermatitis is classified as a type IV (i.e., delayed) hypersensitivity reaction, also known as cell-mediated hypersensitivity. Type IV hypersensitivity reactions result from the interaction between a T-lymphocyte and the specific antigen to which they have previously been sensitized. 

Woman with a red, dry, itching rash on her arms.

What causes contact dermatitis?

Contact dermatitis is caused by exposure to an allergen or irritant, such as detergents, surfactants, extreme pH, and organic solvents. Other irritants include plants from the Anacardiaceae family (e.g., poison ivy, poison oak, poison sumac) and Compositae family (e.g., parthenium, ragweed, aster, sunflower, chrysanthemum, artichoke). Nickel metal, commonly found in belt buckles; fragrances in shampoos and hand soaps; hand sanitizers; latex; and dyes in textiles and cosmetic products, commonly cause contact dermatitis. Contact dermatitis can be acute, the cause of which is typically a strong irritant, or chronic, caused by recurring exposure to a weaker irritant. 

Exposure to the irritant results in an altered epidermal barrier function leading to transepidermal water loss and dry skin. This activation of the immune response leads to cytokine-mediated cell damage. T-lymphocyte sensitization occurs in the induction phase, where the immune system is primed for the allergic reaction and the elicitation phase. During the elicitation phase, the contact allergen crosses the stratum corneum layer of the epidermis and connects with epidermal proteins to form a complete reactive antigen. The dendritic cells recognize and internalize the antigen and transport it to the lymph nodes to present to T-cells. The CD8 and CD4 T-cells trigger an inflammatory immune response and act via direct cytotoxicity and by releasing soluble cytokines, respectively. The dense infiltrates of T-cells contribute to the skin's erythema and inflammation characteristic of contact dermatitis.

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What are the signs and symptoms of contact dermatitis?

The signs and symptoms of contact dermatitis include an erythematous, dry, itchy, or burning rash that can develop within 72 hours after exposure to irritating substances. Vesicles, or tiny, thin-walled sacs filled with clear fluid, ranging in size from pinpoint to five millimeters, are commonly present at the site of exposure. Additionally, the skin can be dry, scaly, and fissured (i.e., cracked). Typically, rashes occur on the hands, arms, legs, and face. Irritation from chemical substances affects the body's most frequently exposed parts, such as the hands. 

Risk factors for contact dermatitis include age and occupation. Infants are at high risk for contact dermatitis due to prolonged exposure to wet diapers. Additionally, the elderly population are at increased risk due to impaired epidermal barrier function, delayed recovery after barrier damage, and decreased epidermal lipid synthesis of skin. Those assigned female at birth are more frequently affected, particularly those between the ages of 20 and 59. Occupational exposure to continuous moisture and repeated hand washing can cause dryness and irritation, increasing the likelihood of contact dermatitis. The occupations with increased risk are healthcare workers, housekeepers, cleaners, and food handlers. Additionally, those who work with chemicals, like beauticians, hairdressers, and construction workers, may be exposed to solvents that cause allergic contact dermatitis. 

How is contact dermatitis diagnosed?

Contact dermatitis can be diagnosed from a physical exam and a thorough patient history. The clinician may ask questions about possible exposure to an irritant or an allergen to narrow the list of potential causes. A trained healthcare professional, such as a dermatologist, can perform a patch allergen test, an investigation to identify specific allergens in allergic contact dermatitis. The individual undergoing testing has approximately 35 patches of allergens systematically applied to their upper back. The patches are typically left in place for 48 hours, which allows adequate penetration of the allergen into the skin. The dermatologist then assesses which allergen(s) cause a slightly swollen, red, itchy rash on the individual’s back. 

How is contact dermatitis treated?

Contact dermatitis is treated by removing or avoiding the triggering allergen. The individual may also be encouraged to stop scratching the area to avoid damaging the skin barrier and causing possible infection. Gloves can be worn to prevent nighttime itching. Over-the-counter calamine lotion and emollients (e.g., Aquaphor, Vaseline) can help reduce dryness and itchiness, and oral antihistamines (e.g., cetirizine) may be used if the pruritus is bothersome. Medications such as topical corticosteroids (e.g., hydrocortisone) can also be applied once or twice daily for two to four weeks or until symptoms resolve. Topical calcineurin inhibitors (e.g., tacrolimus/pimecrolimus) are commonly used in addition to corticosteroids.  

For severe, chronic cases of allergic contact dermatitis, phototherapy in the form of narrow-band UVB radiation and systemic immunosuppression (e.g., azathioprine, mycophenolate mofetil, and cyclosporine) may be prescribed. These medications frequently have side effects, including an increased risk of developing an infection. Therefore, they are reserved for severe cases of contact dermatitis where allergen avoidance is impossible, such as airborne plant contact dermatitis from plants of the Compositae family. 

What are the most important facts to know about contact dermatitis?

Contact dermatitis is a type IV hypersensitivity reaction that occurs when an individual comes into contact with a substance that is an allergen or an irritant. It typically presents as erythematous, pruritic vesicles that commonly emerge on the hands, arms, legs, and face. Common causes of allergic and irritant contact dermatitis include poison ivy, nickel, hair dyes, detergents, latex, and ingredients in hand soaps. To diagnose contact dermatitis, a dermatologist may ask about past exposure to potential irritants and perform allergy testing, explicitly using a procedure called patch testing in cases where the irritant is unknown to elicit a skin reaction. To treat contact dermatitis, the individual may avoid the trigger and avoid scratching the area. Anti-itch creams such as calamine lotion, antihistamines, and other medications, such as topical corticosteroids and calcineurin inhibitors, can be administered to treat pruritus and decrease inflammation. 

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Related links

Contact dermatitis
Type IV hypersensitivity
Papulosquamous and inflammatory skin disorders: Pathology review

Resources for research and reference

Actor, J. K. (2019). Immune hypersensitivities. Introductory Immunology, 103–110. 

American Academy of Allergy, Asthma, and Immunology, American College of Allergy, Asthma, and Immunology. Contact dermatitis: a practice parameter. Ann Allergy Asthma Immunol 2006; 97:S1.

Bauer A, Schmitt J, Bennett C, et al. Interventions for preventing occupational irritant hand dermatitis. Cochrane Database Syst Rev 2010; :CD004414.

Brod, B. A. (n.d.). Management of allergic contact dermatitis. UpToDate. Retrieved July 14, 2022, from 

Fonacier L, Bernstein DI, Pacheco K, et al. Contact dermatitis: a practice parameter-update 2015. J Allergy Clin Immunol Pract 2015; 3:S1.

Fransway, A. F., & Reeder, M. J. (n.d.). Irritant contact dermatitis in adults. UpToDate . Retrieved July 14, 2022, from 

Mowad CM, Anderson B, Scheinman P, et al. Allergic contact dermatitis: Patient management and education. J Am Acad Dermatol 2016; 74:1043.

Prakash AV, Davis MD. Contact dermatitis in older adults: a review of the literature. Am J Clin Dermatol. 2010 Dec 1;11(6):373-81. doi: 10.2165/11319290-000000000-00000. PMID: 20812765.