Q I break out into a rash whenever I use a sunblock or any product that has sun protection factor (SPF). What can I apply to protect my skin from the sun's harmful rays?

A According to Dr Fredric Brandt, an American celebrity dermatologist with his own skincare line, SPF is not an ingredient but a laboratory measure of how effective a sunscreen is.

'The higher the SPF, the more protection a particular sunscreen gives users against ultraviolet rays from the sun,' he tells Urban in an e-mail interview.

The main ingredients in sunscreens, he says, are usually 'aromatic molecules in a specific structure that allow the molecules to absorb ultraviolet rays and prevent them from damaging the skin'.

Products with SPF typically contain a wide mix of ingredients, possibly comprising both naturally derived and chemically based ultra-violet blockers.

So there is a wide range of possible factors as to what you are allergic to. Without knowing exactly what you are sensitive to, recommending a product that you can use safely and without an allergic reaction is extremely difficult, says Dr Brandt.

The best course of action would be for you to do an allergy or patch test with a dermatologist so as to determine the extent of your allergy and which sunscreen ingredients your skin is sensitive to.

A dermatologist will also be able to recommend what sun protection products you should use. In the meantime, I recommend using a nice, big umbrella when you go outside.

This article was first published in Urban, The Straits Times.