Q. I am allergic to the SPF [sun protection factor] in the many – not cheap - mainstream skin care and cosmetic products I have tried over the years including children/baby products. I have never known what ingredients to look for as no one seemed to know.  I even called one of the sunscreen makers who said they had never heard of my problem. A. That’s odd, in our opinion, as it is well known that some synthetic (or semi-synthetic) chemicals used in sun preps can irritate sensitive skin. It is categorized as a ‘not uncommon reaction’ in one study.

There are two basic types of sun protection: the first uses chemicals as protection against UV damage and the second contains a physical barrier – usually a mineral/s such as titanium dioxide or zinc oxide. As we said, it is more usual for the first type to trigger sensitivity.

The natural skincare company, Green People (www.greenpeople.co.uk), whose products we frequently recommend to readers in your situation, offer the following explanation:

The chemical sunscreens can cause two types of reaction:

• contact allergy leading to symptoms of dermatitis, typically a red, itchy rash, which occurs regardless of whether the chemical sunscreen is exposed to sunlight or not.  The dermatitis is found in areas of skin covered by sunscreen, but not necessarily exposed to the sun.

• photocontact allergy, which occurs when the chemicals in the sunscreen - after it penetrates the skin - are changed by the UV rays and then produce an allergen. The symptoms arise when one is in contact with the chemical and simultaneously exposed to sunlight. An article in the journal Dermatitis says that sunscreen is one of the most common causes of photoallergy.

The chemical sunscreens that are most frequently reported as the cause of allergies are octocrylene, benzophenone-3, benzophenone-10 and octyl methoxycinnamate (OM).

Green People use titanium dioxide with a secondary filter of isoamyl p-methoxycinnamate to boost UVB protection without leaving a white veil on the skin. While it sounds similar to octyl-moethoxycinnamate, isoamyl p-methoxycinnamate is a natural compound, found in the roots of the Indian galangal plant, a member of the ginger family. Commercially, it is prepared from cinnamic acid, found in the leaves of the cinnamon tree and is chemically identical to the original natural molecule. Green People is not aware of any reported skin reactions to this ingredient.

That all sounds a bit complicated but the bottom line is that, in our experience, people whose skin reacts to chemical SPF’s generally do not have a problem with physical mineral barriers.

Finally, we should add that between the time of this reader’s query and going to press, Green People sent samples of their sun protection products, which contain a high proportion of organically certified ingredients, to this reader to try. She wrote to us saying that she is ‘delighted with the result’.

Green People Scent Free Sun Lotion SPF25 for sensitive skin/£18.95 for 200ml and try-me size £5 for 20 ml - buy here