Hello Antoinette, Your son seems to be having a type of eczema called atopic dermatitis. It is a type of skin allergy which has remissions and relapses.It is good that you have already identified certain exacerbating factors and you are avoiding them. Sunscreens have a lot of ingredients in them. Apart from the chemical and physical sunscreen components, they also have patabens, certain preservatives and emulsifiers. The most common components in a sunscreen which could cause allergy are para amino benzoic acid (PABA), avobenzone and parabens. Ideally you need to do a test called patch test to detect the causative allergen. If not , you could use a physical sunscreen which has zinc oxide or titanium oxide after consulting your dermatologist. Reapply every 3 hours and physically cover with a broad rimmed hat, full sleeve clothes, etc. That would be the best solution for an allergic person. Hope this helped. If you have further queries, please feel free to contact me.