It is difficult to diagnose any skin lesion without being able to see the lesions. However, from your description, I feel it might be a measles rash or some kind of allergy/dermatitis.
However, if you've already had measles, you won’t be affected by it again as the body develops sufficient immunity to combat the infection. It is seen among those who haven't been vaccinated in the early years of life.
Measles rash is highly contagious and usually begins in the chest, face, behind the ears and spreads to other parts of the body. But it has other associated signs and symptoms such as cough, runny nose, inflamed eyes, sore throat, fever and a red, blotchy skin rash.
Hives or urticaria causes red and sometimes itchy rash on the body such as face, neck, trunk, arms, and legs and perhaps anywhere on the body. They are usually allergic (food, medication and insect stings) but may also be due to infections and stress. Many a times no specific cause for them is ever found. They usually go away on their own, but in sometimes oral antihistaminics (such as cetirizine, loratidine, benadryl available over the counter) may be needed.
However, if the symptoms persist or increase in frequency or intensity or you experience any fever, cough or difficulty in breathing or sweating etc, you should immediately consult a dermatologist for proper treatment.
Do write in if you need any other information.
Thank you ever so much.
I shall make an appointment.