hi dear, first thing bruise
wont last for 4 month, so its not that. sun allergy
should be on entire face, not on one spot, same goes for cosmetics. also if it is any type of allergy there must be some itch. so what i feel is that it is a kind of nevus
, i mean a kind of mole which appear late in life. so i suggest you to meet a dermatologist
and get checked what it is.