Poison ivy

Alternative names
Dermatitis - contact; Allergic dermatitis; Dermatitis - allergic; Contact dermatitis; Poison oak; Poison sumac

Definition
Contact dermatitis is an inflammation of the skin caused by direct contact with an irritating substance.

Causes, incidence, and risk factors

Contact dermatitis is an inflammation of the skin caused by direct contact with an irritating or allergy-causing substance (irritant or allergen) vary in the same individual over time. A history of any type of allergies increases the risk for this condition.

Irritant dermatitis, the most common type of contact dermatitis, involves inflammation resulting from contact with acids, alkaline materials such as soaps and detergents, solvents, or other chemicals. The reaction usually resembles a burn.

The second most common type of contact dermatitis is caused by exposure to a material to which the person has become hypersensitive or allergic. The skin inflammation varies from mild irritation and redness to open sores, depending on the type of irritant, the body part affected, and the sensitivity of the individual.

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

Common allergens associated with contact dermatitis include:

     
  • Poison ivy, poison oak, poison sumac  
  • Other plants  
  • Nickel or other metals  
  • Medications       o Antibiotics, especially those applied to the surface of the skin (topical)       o Topical anesthetics       o Other medications  
  • Rubber  
  • Cosmetics  
  • Fabrics and clothing  
  • Detergents  
  • Solvents  
  • Adhesives  
  • Fragrances, perfumes  
  • Other chemicals and substances

Contact dermatitis may involve a reaction to a substance that the person is exposed to or uses repeatedly. Although there may be no initial reaction, repeated use (for example, nail polish remover, preservatives in contact lens solutions, or repeated contact with metals in earring posts and the metal backs of watches) can cause eventual sensitization and reaction to the product.

Some products cause a reaction only when they contact the skin and are exposed to sunlight (photosensitivity). These include shaving lotions, sunscreens, sulfa ointments, some perfumes, coal tar products, and oil from the skin of a lime. A few airborne allergens, such as ragweed or insecticide spray, can cause contact dermatitis.

Symptoms

     
  • Itching (pruritus) of the skin in exposed areas  
  • Skin redness or inflammation in the exposed area  
  • Tenderness of the skin in the exposed area  
  • Localized swelling of the skin  
  • Warmth of the exposed area (may occur)  
  • Skin lesion or rash at the site of exposure       o Lesions of any type: redness, rash, papules (pimple-like), vesicles, and bullae (blisters)       o May involve oozing, draining, or crusting       o May become scaly, raw, or thickened

Signs and tests

The diagnosis is primarily based on the skin appearance and a history of exposure to an irritant or an allergen.

According to the American Academy of Allergy, Asthma, and Immunology, “Patch testing is the gold standard for contact allergen identification.” Allergy testing with skin patches may isolate the suspected allergen that is causing the reaction.

Patch testing is used for patients who have chronic, recurring contact dermatitis. It requires three office visits and must be done by a clinician with detailed experience in the procedures and interpretation of results. Patients should bring suspected materials with them, especially if they have already tested those materials on a small area of their skin and noticed a reaction.

Other tests may be used to rule out other possible causes, including skin lesion biopsy or culture of the skin lesion (see skin or mucosal biopsy culture).

Treatment

Initial treatment includes thorough washing with lots of water to remove any trace of the irritant that may remain on the skin. Further exposure to known irritants or allergens should be avoided.

In some cases, the best treatment is to do nothing to the area.

Topical corticosteroid medications may reduce inflammation. Carefully adhere to instructions when using topical steroids because overuse of these medications, even low-strength over-the-counter topical steroids, may cause a troublesome skin condition. In severe cases, systemic corticosteroids may be needed to reduce inflammation. These are usually tapered gradually over about 12 days to prevent recurrence of the rash.

Wet dressings and soothing, antipruritic (anti-itch), or drying lotions may be recommended to reduce other symptoms.

Expectations (prognosis)
Contact dermatitis usually clears up without complications within 2 or 3 weeks but may recur if the causal agent cannot be identified or avoided. Change of occupation or occupational habits may be necessary if the disorder is caused by occupational exposure.

Complications

Secondary bacterial skin infections my occur.

Calling your health care provider
Call your health care provider if symptoms indicate contact dermatitis and it is severe or there is no improvement after treatment.

Prevention
Avoid contact with known allergens. Use protective gloves or other barriers if contact with substances is likely or unavoidable. Wash skin surfaces thoroughly after contact with substances. Avoid overtreating skin disorders.

Johns Hopkins patient information

Last revised: December 5, 2012
by Potos A. Aagen, M.D.

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