Intense Pulsed Light (IPL) is typically used for hair removal or to treat discoloration of the skin. Redness after a treatment is typical, but significant swelling sounds unusual. Are you be using a new skin product that could be causing allergy?
I'm sorry you're having this problem, but the IPL light does not penetrate through the skin to affect the underlying fat.
If you're not satisfied with the explanation from your physician, please get another opinion from a physician that regularly performs IPL treatments.
I hope this helps, and best regards.