My daughter (almost 18 months old) has really bumpy skin. It isn't red like a rash, it isn't exactly scaly like dry skin (although sort of), it is almost like tiny goose-bumps. It is primarily concentrated down the sides of her back, the side of her belly, a patch on the front of each thigh, and usually a patch near each elbow. Lately too she has been getting a red/dry patch around her mouth, but it comes and goes very quickly.
Dd gets KP on her torso like you describe when she gets butter (but not ghee or raw goat kefir). If you do a search, there are a couple threads around. It's also associated with some nutrient deficiencies - I think vit A, mag, biotin possibly? Perhaps calcium too? It's been a while, but those threads would have the specifics.
It is likely KP...my DD gets it. She tends to have it most of the time, but allergens definitely cause it to flareup, especially on her cheeks. Give her yogurt and the next day her face looks really awful.