['Among factors that may affect the potency of botulinum toxin A (Botox), it is said that foam, together with bubbles, may cause surface denaturation of the toxin.', 'To determine whether the muscle relaxation effect of Botox is preserved and has the same duration when it is reconstituted in the presence of foam.', 'Six female volunteers, aged 42 to 56 years old, were treated for glabellar and periocular wrinkles. Each half of the face was treated with 16 U of Botox divided in four sites: three at the lateral orbital area and one at the medial brow, in the glabellar region. The right side received Botox gently reconstituted with saline to avoid foaming formation. The left side of the face was treated with Botox that was rapidly reconstituted in order to achieve as many bubbles as possible, even with shaking. Blinded observers compared pretreatment and posttreatment photographs and answered assessment-related questions. The results were analyzed clinically and statistically.', 'There was no difference in muscle paralysis between treated sides in all patients, neither in early (15 days) nor late (4 months) follow-up evaluations.'] Does foam during reconstitution affect the potency of botulinum toxin type A?