Hi Erla,

Do you mean sunburn as in blisters and redness?  If so, I have no experience of this. 

However if you mean browning/tanning of the skin (too easily), this can happen if the release of ACTH from the pituitary gland is excessive, thus causing elevated melatonin levels. Sometimes if the CAH is not under good control or before diagnosis and treatment this can happen. The result may be patchy hyperpigmentation particularly in skin folds, scar lines, scrotal or vulval tissue, neck etc. or an all over tan.

This burning could much more likely be from the PKU. As I understand it, people with PKU usually have very fair hair and skin....yes/no?