Does anyone know why my 3.5 month old baby has red palms? We took like a 15 minute walk and he was…

Does anyone know why my 3.5 month old baby has red palms? We took like a 15 minute walk and he was down to his diaper during the walk. He wasn't too too hot but he was a little bit sweaty. Waited till almost sundown to go so it wouldn't be too hot on him. Never saw my other kids have thia...do you think it's from the heat? There are no sores or anything like Hand, Foot, Mouth Disease either...Thanks in advance!