Depending on what caused the rash, you can try different lotions and creams.
If it's hives, you'll need an antihistamine. For heat rash, any sort of lotion will help.
Fresh air helps the most. Try to wear only a housecoat around the house as much as possible.
It depends on what the cause is.
If it's from heat rash, you could use any sort of "baby lotion", or cream/ointment.
If it's chicken pox...forget it.
If it's pimples ( which 99% of the population gets ) there is no "cure".
If it's "hives" from an allergy, you will need to figure out what you are allergic to . If it's on the bottom, it's more than likely a laundry detergent to blame.
Sitting tends to make any sort of rash worse...so keep on your feet more.
Fresh air also helps, so wear a housecoat around the house, and nothing more.