Laser treatment on chin and neck.

Hello doctor last year my wife suddenly got black patches lykwise birthmark on her chin and neck... Been to a dermatologist in april'17 he said it's because of allergic reaction through a medicine mostly same happens with medicine tz and ofloxocin. Whereas i remember i only given her norfloz tz, ofloxocin (O2) and mahacef may be she got marks from any of these but im not sure but i guess it happens only after giving any of these mdicine.He prescribed evion vitamin e capsule and epi 1000 vitamin c tablet and metasone s and halox s tube for application its been 4 months stil not much improvement. So can i go for laser treatment or anyother option?? What are the sideeffects of laser lykwise i heard u hav to avoid sun exposure, there are chances for skin cancer, skin gets depletes nd all so is that true?? should i go for laser or not or any better medicine to recover from it. and one more thing is there any way through which i get to know from which medicine she is allergic ??