What are these?

So like 2-3 years ago I noticed I have these spots mostly around my neck/collarbone and I have no clue what they are. They don't itch or anything , they are just there. Sometimes they disappear entirely, sometimes they just move on from one spot to another. What I've seemed to notice is whenever I go on vacations where I swim a lot it usually disappears entirely and only comes back like half a year later. If not on vacation I use Tea Tree Oil on it which seems to make it go away for like a month until they come back again. If it matters I change clothes ever day and I do bath daily , and my bed sheet gets washed every 2 weeks, so I'm thinking it's some kind of allergy. Anyone knows what these are?

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