4 months after co2 laser resurfacing I seem to be developing an allergy to all sun screen products (even baby sun screen).

What you are experiencing is not unusual after laser resurfacing. You can be given oral antibiotics or oral natural, anti-inflammatory supplements to help with this. Try Elta MD Clear sun block which is formulated with zinc and niacinamide for anti-inflammatory action and is also very lightweight.

What you are experiencing is not uncommon after CO2 laser resurfacing.  Many times patients will experience breakouts a 2-3 months after their procedure.  If the problem becomes widespread, a course of doxycycline as stated prior, would help the situation while your skin normalizes.  I would also suggest a zinc based sunscreen.  Good Luck

It is very common for the skin to have break-outs after CO2 although this commonly occurs at about 4-6 weeks post-op.  If it persists you may benefit from taking doxycycline for a while until the glands all settle down.  Many products can irritate this new skin.  Look for a sunscreen that has zinc as the sunblock.  It is better for a total block after laser, and is usually less irritating than the sunscreens.