There isa wide variety of conditions that are known tocause an itchy rash on the skin, includingallergic reactions to medication, contact dermatitis as a result of poison ivy exposure, ring worm, viruses such as varicella-zoster, insect bites, hives and yeast infections, according to thethe American Academy of Family Physicians. Doctors will typically use other factors to make a diagnosis other than the mere presence of itching and rash, including the size, shape and color of a rash, as noted by theAmerican Academy of Family Physicians.
For example, if an individual experiences an itchy rash shortly after taking a medication, the American Academy of Family Physicians indicatesthat this may be an allergic reaction to the medication. Some itchy rash conditions, such as pityriasis rosea, or Christmas tree rash, may go away on their own without special treatment, according to the Mayo Clinic. Other causes of itchy rash, such as lichen planus, may require treatment in severe cases, though can be treated with over-the-counter remedies such as aloe vera, the Mayo Clinic advises. Psoriasis is an example of an itchy rash condition that the Mayo Clinic describes as being potentially harmful to a patient's quality of life.