Which is more effective, combining tretinoin and benzoyl peroxide or tretinoin and erythromycin?

Depends: Using tretinoin and benzoyl peroxcide can be effective- both individually can cause redness and photosensitivity. Using them together may increase this tendency- you may need additional moisturizer and/or sunscreen. The tretonin/erythromycin combination may be less irritating. It is best to check with your doctor to determine which combination is best to try.

May vary by person: The effectiveness of various treatment regimens will vary by individual and sometimes best determined by trial and error. I would recommend the tretinoin and benzoyl peroxide because resistance to the later is less likely than erythromycin.

I'd suggest the: Combo of the tretinoin and benzoyl peroxide first. I try to stay away from long-term antibiotics, unless everything else fails to work.