PRP has been used to treat acne scarring, alopecia (especially in women), and non-healing ulcers. It is also effective for skin rejuvenation and tightening around the eyes, cheeks, thinning of the skin on the neck, back of hands, and other areas including post-pregnancy skin laxity. The platelets secrete growth factors, including platelet-derived growth factor and vascular endothelial growth factor, both of which have positive effects on hair growth and skin rejuvenation. Platelet-rich plasma is injected by multiple tiny punctures under the dermis. These are usually performed 2 to 4 weeks apart. Minimal swelling, bruising, and redness for the initial 12 to 24 hours are expected. A bruise at the needle stick site may be visible for 2 to 3 days.