Can a professional chemical peel make old scars worse?

Thats very difficult to answer without a picture and/or examining you.
Peels can cause burns, scars and pigmentation.  It really depends in what type of peel is used and what strength.  Then the other variables are your skin type and if you are on any medication or if you have had any other skin treatments.
Your practitioner should be the best to answer those questions.

Our treatments use combination therapy to improve the epidermis and dermis for most deep scars. The options available for acne scars depend on the character of your scars, in terms of topography and contour. We see atrophic and hypertrophic acne scars, as well as scars that have hypo and hyperpigmentation. We begin each scar evaluation with an assessment of scar quality and subtype. Our main concern is rebuilding collagen and that is why we use a HIDEF protocol that includes combination therapy. Morpheus 8, scar subcision, fibrous release, fractional laser, CO2 laser, Thulium laser, PDL Vbeam laser, and fractional resurfacing can be used in addition to TCA Cross and chemical peels to further improve skin. Patients should start Melarase AM and Melarase PM for active hyperpigmentation. Always begin with a consultation to decide whether early subcision should be started.

Best,
Dr. Karamanoukian
Realself100 Surgeon

Hello and thank you for your question. Chemical peels (light or aggressive) should not make your scarring worse, but you may need to combine these treatments with a skin resurfacing laser as well to achieve the best results.I prefer to use the Perfect derm Peel and then 4 weeks later either do PRP micro needling or a fraxel treatment. Best of luck!

Hi mitsuki, In general, chemical peels do not make old scars worse. The stronger the medical-grade peel, the more impact it has on scars. Microneedling with PRP, works best on flat scars. However for raised scars, both of these modalities aren't effective.On the third day, you can start using cleansers like SkinMedica Sensitive Cleanser or Facial Cleanser and use a strong hydrating cream like Dermal Repair. Don't use retinols, astringents, Vitamin C or other acids.All the best, Justin Harper, M.D.

Chemical peels can be superficial to deep depending on the type done. Scars typically are very deep and are not effected much by peels.
Microneedling can get deeper into and through scarring often to help heal through an old scar.
Good noncomedogenic hydrators/ topicals Help with recovery from peels.
Best. Dr Brecht 
Seattle, Wa