It is not usually necessary. But if a heat rash recurs more than occasionally, it could be an allergic rash which is made worse (but not caused) by the heat.

It might then be wise to see a doctor. These rashes include photosensitive dermatitis (an itchy rash brought on by exposure to ultraviolet light) and nettle rash which can be an allergic reaction to sweat.

There is a similar sort of rash to heat called intertrigo, which may require medical attention. It is a red, raw rash which develops in the creases of the skin, especially in the groin area. It is much more likely to occur among obese people.

None of these rashes looks like heat rash although they may feel the same to the sufferer.