Botulinum toxin treatment is the injection of a substance that temporarily reduces the contraction of the muscle it is aimed at. Lines between the eyebrows and excessive sweating of the armpits are among its licensed (approved) uses; areas such as the forehead and crow's feet are also considered, but some of these are outside the licensed uses. It is not given during pregnancy, breastfeeding or in certain nerve–muscle diseases; the effect usually begins within 3 days, settles in 10–14 days and lasts an average of 3–4 months.
A dermal filler is the general name for substances applied under the skin to replace lost volume in the face, address lines and shape the face. Hyaluronic acid (a molecule found naturally in the body that holds water) is the most commonly used. How long it lasts varies with the substance, the area and lifestyle. The blood vessels of the face are complex: an injection made in the wrong direction can cause a pulmonary embolism (blockage of a blood vessel in the lungs).
Mesotherapy is a procedure carried out with small-volume injections into the skin and beneath it. In skin rejuvenation it is one of the methods that aim to stimulate the production of collagen (the structural protein that gives the skin its strength); it seeks to increase the skin's own collagen by stimulating fibroblasts (collagen-producing cells). It does not give instant volume like a filler; results need a period of 3–4 months to become visible. Sun protection and stopping smoking also shape the result.