I would try calamine lotion or Aloe Vera gel, cool light clothing (natural material like cotton, linen or bamboo) and cold water baths

I would recomend keeping him cool and giving his regular baths that aren’t too warm to soothe and wearing minimal clothing might help

Curassow is really good. Cornflour does the same thing for half the price tho

Bicarb soda in a warm bath soothes and clears skin complaints and is safe for baby

You need to treat the cause and not the symptoms. If baby is hot, cool them down. a wet flannel on the back of the neck shoudl help