Sunscreen is necessary to avoid the sun's harmful rays, but if you are sensitive to creams and lotions, wearing it may be difficult. If you experience redness, swelling and/or blisters just minutes or even days after applying it, you may be experiencing contact dermatitis (the term meaning a skin reaction to a substance). If the reaction is severe, call a doctor immediately. But there are a few things you can do for instant treatment.
Remove any traces of the sunscreen. Wash your body with a mild cleanser and water. Use a washcloth to gently wash the sunscreen off your skin. Do not harshly rub, as this will only cause further irritation.
Lightly and gently apply a hydrocortisone cream, which is available at your local drugstore. This will help calm the skin down and take away some of the redness.
Call a dermatologist for further testing. Be sure to bring in the product with you. He can check to see which substances you are allergic to through various allergy testing materials. It may be that you are allergic to the fragrances or dyes found within that particular sunscreen.