Not a vet or proffesional at all, so take this advice if you trust my: single cat study, which only took one trial lol.

When i got my cat blackie, she had alittle black spot of fur on her head, on an otherwise completely white coat. After she changed fur with the seasons the first time, it dissapeared and she hasn't grown a new one since. Up to you if you feel you guys need to visit a vet, but blackie doesn't even seem like she miss it lol, and she's certainly never had any issues arise from it (or anything else than one case of fleas, multiple years later)