A rash is an area of irritated, swollen and often red skin. Rashes may be itchy, bumpy, scaly, crusted or blistered, as described by the National Institutes of Health. Rashes may appear quickly, or develop over time. Some rashes will resolve on their own while others may require treatment. There are many different kinds of rashes with as many different causes.
Allergic Contact Dermatitis
Allergic contact dermatitis is a rash that occurs when the skin becomes sensitive to a specific substance that comes into contact with the skin. Allergic reactions are the body's abnormal response to a normal substance, such as nickel, rubber products or plants like poison ivy.
This type of rash typically appears 48 to 72 hours after exposure to the allergen, according to Skin Sight. The rash appears as a red, itchy and swollen skin patch that can turn into small blisters. The blisters may break and crust over leaving scabs where the rash was.
The best treatment is to avoid contact with the allergen. When the rash does occur it can be treated with steroid creams or oral antihistamine medications.
Irritant Contact Dermatitis
Irritant contact dermatitis is a rash that appears within a few hours of contact with a strong chemical irritant. This type of rash is not due to an allergic response but is an inflammatory response triggered by chemical injury to the skin. This rash looks like raised blister-like bumps and may be itchy, burn or sting. An irritant contact dermatitis rash will resolve once the skin heals from the injury. Applying petroleum jelly can help to ease the pain of the rash.
Drug Eruption Rash
An adverse response to a medication can cause a drug eruption rash. A drug eruption rash may cover the entire body and can vary in appearance. Some rashes only produce small pink or red bumps and other may trigger hives. This type of rash should be treated by a medical professional as the medication that triggered the reaction should be stopped under a doctor's care.
Ptyriasis rosea is a rash often of unknown cause that can last for 6 to 8 weeks as reported by Skinsight. This type of rash usually affects the upper body including the back, chest and arms but can also on occasion occur on the thighs.
Ptyriasis rosea begins as a small red, scaly looking patch of skin that spreads. Many patients experience a period of general ill feeling, with muscle aches, congestion and headache, just before the onset of the rash. Pryriasis rosea does not require treatment as it resolves on its own after the 6 to 8 week period.
Skin lesions that look like a small, red, thread-like line that are very itchy may be due to scabies. Scabies is a skin infection caused by a mite known as Sarcoptes scabiei var. hominis. This mite, which is contagious, burrows under the skin and triggers an allergic reaction in the body. This allergic reaction creates pink to red bumps that look like bug bites but when accompanied with the above mentioned lesions is a tell-tale sign of scabies infection. Scabies will not improve without specific medical treatment.