Poison ivy grows as vines or low shrubs in most climates. Each leaf on a poison ivy plant has three smaller leaflets. Touching any part of the poison ivy plant can cause red, swollen skin, blisters and severe itching, sometimes within hours after exposure.
A poison ivy rash usually resolves on its own within a few weeks. In the meantime, soothe irritated skin with an over-the-counter topical treatment, such as calamine lotion. Oatmeal baths and cool compresses also might help. Talk to your doctor if you have a severe poison ivy rash or if the rash involves your face or genital area.
Poison oak, poison sumac and the fruit rind of mangoes cause a similar rash.
Ragweed plants typically bloom in the United States in the fall. Ragweed pollen is a primary cause of hay fever (allergic rhinitis).
For those who are allergic to ragweed, exposure to the plant pollen through touch or airborne contact can also cause a rash. You might notice itchy red streaks on the skin or swelling of the eyelids. A ragweed rash usually develops within two days of exposure and resolves on its own within three weeks, as long as you avoid additional ragweed exposure.
In the meantime, control itching with an over-the-counter anti-itch cream, such as hydrocortisone cream, and an over-the-counter antihistamine if needed. Talk to your doctor if the rash is painful or lasts longer than three weeks.
Wild parsnip grows in sunny areas, often along highways and in prairies. The plant bears large clusters of yellow flowers on a thick stem. Touching sap from the wild parsnip plant — combined with exposure to sunlight — can cause a burn-like skin reaction. Within a day after exposure, the skin turns red and might develop painful blisters. While mild reactions might go unnoticed, a severe reaction can cause skin discoloration for months or years.
Soothe the affected area with a cool, wet cloth or moisturizer. Talk to your doctor if the reaction is painful or the blisters are severe or last longer than a couple of weeks.
Heat rash (miliaria)
Heat rash or prickly heat develops when blocked sweat ducts trap perspiration under your skin. Miliaria rubra (A), one type of heat rash, appears as red clusters of small blister-like bumps that can be itchy. Miliaria crystallina (B), another type of heat rash, appears as clear, fluid-filled bumps.
Heat rash isn't serious and usually resolves quickly when the affected area cools. In the meantime, reduce sweating by staying in an air-conditioned space or using fans to circulate the air. Wear lightweight clothing and limit intense physical activity. Apply cool compresses or soak in a cool bath for greater relief.
Polymorphous light eruption
Polymorphous light eruption is a rash that occurs due to sensitivity to sunlight (photosensitivity). Within hours of sun exposure — usually in the spring or early summer — you might notice an itchy, red rash in sun-exposed areas. The spots occur most often on the upper chest, neck and the back of the arms.
The rash usually resolves on its own within a few days, although the condition can occur again. In the meantime, limit sun exposure and wear sun-protective clothing and sunscreen. An over-the-counter anti-itch cream, such as hydrocortisone cream, might help ease discomfort. Talk to your doctor if the reaction is severe or painful.
Tinea versicolor is a common fungal infection that causes patches of discolored skin. Tinea versicolor is most common in warm, humid weather. The patches — which can be white, brown, red or gray-black — might be mildly itchy and are often more noticeable after sun exposure. In adults and adolescents, the patches usually develop on the back, chest or arms. In children, tinea versicolor usually affects the face.
Treatments include over-the-counter antifungal creams, lotions or shampoos. Skin color might remain uneven for months, however, and the infection might return — especially in warm, humid weather.
Swimmer's itch is an itchy rash caused by certain parasites that normally live on waterfowl and freshwater snails. On warm, sunny days — especially in calm freshwater lakes or ponds — these parasites enter the water. While you swim, the parasites might burrow into your skin. The parasites soon die — and you have itchy, red, raised spots on your skin.
Swimmer's itch is usually mild and resolves on its own within a week. In the meantime, control itching with an over-the-counter anti-itch cream, such as hydrocortisone cream. However, if initial itching is severe, scratching can cause abrasions and skin infections. Talk to your doctor if symptoms persist longer than three days.
Chiggers are tiny mites found in tall grass and weeds. If you brush against infested plants, chiggers might attach to your pant cuffs or shirt sleeves and make their way onto your skin. They fall off after a few days, leaving behind clusters of itchy, pink bumps. When scratched, chigger bites can become red and crusty.
Chigger bites usually heal on their own within one to two weeks. Vigorously scrub the area with soap and water to remove the mites. Control itching with calamine lotion or an over-the-counter anti-itch cream, such as hydrocortisone cream. Placing plastic wrap around the area treated with hydrocortisone cream might help soothe itching.
Lyme disease is a tick-borne illness that causes a distinctive rash, flu-like symptoms and aching joints. The rash begins as a small, red bump (A) that appears after a tick bite. Over the next few days, the redness expands and might resemble a bull's-eye (B). Fever, fatigue and a headache are a few of the symptoms that might accompany the rash.
If you suspect that a tick bit you and you experience signs and symptoms of Lyme disease, contact your doctor immediately. Treatment is most effective when started early. Left untreated — even if the signs and symptoms resolve on their own — Lyme disease can cause serious complications involving the joints and nervous system.