Are you breastfeeding? Allergens can also be passed on from your milk to your baby. when I was breastfeeding and ate peanuts, my boy will break into a rash after drinking my milk.
Other than pumpkin, is there anything new that you started? Like biscuits?
Usually heat rashes will subside if you keep the area cool and clean.
Allergic reactions from food usually occur 10-15min or up to an hr after the food is fed.