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

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.  

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

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.