What’s That Rash?

Almost everyone gets a rash now and then. Many are simple and can be treated successfully at home, but if you’re at all in doubt or concerned, see a doctor for diagnosis and treatment.

What does require immediate medical attention, however, is if you have a rash that is accompanied by difficulty breathing or a feeling like your throat is closing up, high fever, increasing or severe pain (particularly in the neck or head), swelling of the face or extremities, vomiting or diarrhea, dizziness or confusion.

Now here are some of the most common types of rashes, how you get them, and what to do about them:

Contact Dermatitis

Even if you’ve never experienced it, you’re probably aware that contact with poison ivy, poison oak, poison sumac and other toxic plants can result in a skin rash. But there are a number of other sources of simple contact that can readily bring on redness and inflammation with a rash that itches and can be weepy, blistered or dry and flaky. Some of these include:


  • dyes in clothing or other fabrics
  • soaps, cosmetics and similar personal products
  • hair dye and other hair products
  • latex or rubber
  • household or industrial chemicals


If you know the possible cause, avoid it and see if the rash clears up on its own or with an over-the-counter topical treatment. If it doesn’t, a visit to the dermatologist is in order.

Insect Bites

Many insect bites and stings can bring on redness, swelling and itching. Flea bites, for instance, appear as tiny, very irritating and itchy red dots. Microscopic mites cause a condition called scabies, with a rash and intense itching. Over-the-counter medications will take care of most of these reactions, but see a doctor if you’ve been bitten by a tick that could transmit Lyme disease. (Not all tick bites are suspect; 95 percent of cases of Lyme disease in the U.S. have occurred in the northeast and upper Midwest.)

Allergic Reactions

A rash may be a side effect or allergic reaction to a medication. For example, some antibiotics can cause increased sensitivity to sunlight, resulting in a rash that looks like sunburn. A rash may also be a sign that you’ve developed a food allergy. Allergic reactions like these usually appear within minutes or just a few hours of ingesting the allergen. If you suspect a food allergy, skin patch tests can confirm it.

Hay fever is an allergic reaction to plant pollen in the air and can cause a rash with itchy red patches similar to hives. Other symptoms are like those of the common cold, with a runny nose, sneezing and watery eyes. You should find relief with a simple antihistamine from the drug store.

Bacterial and Viral Infections

Bacteria and viruses can cause rashes that vary considerably with the causes. All of them are contagious and require prompt medical attention for successful treatment. These infections include herpes, impetigo, measles, rubella (German measles), chicken pox, mononucleosis, strep throat, scarlet fever, rheumatic fever and in rare cases toxic shock syndrome.

Shingles is caused by the same virus as chicken pox and shows as a blistery rash on one side of the body. It’s caused by a reactivation of the virus that has lain dormant in adults who had chicken pox previously, but it can be transmitted to those who haven’t. Shingles can be treated with professionally prescribed oral medication. Vaccination to prevent this painful condition is recommended for everyone over 50.

Fungal Infections

Fungi cause a variety of rashes including the highly contagious athlete’s foot and ringworm as well as the yeast infection known as candidiasis. These can all be treated with topical or oral antifungal medications.  

Autoimmune Conditions

For reasons yet to be fully understood, the body’s immune system will sometimes turn on itself and attack its own tissues, causing conditions like eczema (atopic dermatitis), psoriasis, lupus and other disorders the symptoms of which include rashes. Because there are many dozens of autoimmune conditions and many of them have similar symptoms, diagnosis is something you can’t do yourself, and it’s important to see a doctor for proper treatment.

Hard as it may be to resist, the one thing you shouldn’t do with any itchy rash is scratch it because scratching can break the skin and cause infection to spread.