Acne scars are of different types and there is no single treatment that acts on all types. Scars occur due to inflammation while acne is healing. There may be excess pigment deposition turning skin black, blood vessel distortion turning skin red, or extra/deficient skin formation leading to depressed and raised scars.

Mederma contains onion or allium cepa extract which has an antibacterial and anti inflammatory property. If applied during the healing of acne or while scar is red and itchy, it can reduce the inflammation and the severity of the scars. But it has minimal effect on pigmentation and cannot effectively treat black spots. Also, old acne scars with textural defect where there is no active inflammation do not respond to onion extract at all.

Thus such creams can be used as an adjunctive treatment along with other medicines and procedures to improve active acne and scars, but they cannot heal all scars on their own with solo use. Please visit your dermatologist to know what treatment will be the best for your acne marks and scars and whether you can expect any improvement with onion extract creams.