A good doctor will always assess a patient's health for any conditions that might put the patient at a higher risk during an aesthetic procedure, says Dr Walter King Wing-keung. For example, patients taking blood thinners may be at higher risk for any injection therapy or laser treatment and may have more bruising and swelling. Diabetics may be more likely to get infections. People with lupus should not try laser or light treatments as this may stir up underlying conditions. "Experience and special training is necessary [for doctors administering aesthetic procedures] to minimise and lower the complications and side effects," says King. Here's a look at the trendy treatments in Hong Kong and their possible side effects. BOTOX What it does Injections of this substance block muscular nerve signals, which weakens the muscle so that it can't contract and diminishes your unwanted facial wrinkles. Can also reduce sweaty armpits or palms. Be warned The side effects, such as drooping brows or eyelids when too much is injected, usually last no more than two months, says King. According to the American Society of Plastic Surgeons, the toxin can spread beyond the treatment area, causing signs and symptoms such as breathing problems, trouble swallowing, muscle weakness and slurred speech. But this is very rare. HYALURONIC ACID What it does A natural substance found in the body, when this gel is injected, it acts like an inflated cushion to support facial structures and tissues that may have lost volume or elasticity due to ageing. It also brings water to the surface of the skin, to keep it looking fresh and supple. Be warned "If not carefully administered, the filler can go into the blood vessel and cause tissue damage," King says. There may be allergic reactions. POLYLACTIC ACID What it does A non-toxic and biodegradable synthetic filler that is injected into the face, causing the body's own production of collagen. It's known to work particularly well filling the lines caused by laughing, augmenting thin lips and filling out deep nasolabial folds. The only brand approved by the US Food and Drug Administration is Sculptra Aesthetic. Be warned Risks can include haematoma, or blood pooling beneath the skin. Although rare, infection and necrosis, or skin loss, is possible. There's also a risk of the particles forming lumps that can be felt or seen beneath the skin, which can occur months later. STEM CELLS AND GROWTH FACTOR BEAUTY TREATMENTS What it does Claims the injection of stem cells or application of "miracle" creams can erase wrinkles and produce younger, fresher skin. Be warned Possible consequences include anaphylactic shock, especially for those who have hypersensitive reactions. Stem cells cannot be used as a cream, lotion or serum because they will die and the product, which consists mainly of growth factors, has an extremely low amount of stem cells anyway. "Our body is a very complicated machine. Even for just for the skin, we are still discovering new functions of cells and new signal pathways between cells all the time, which means we still do not have the complete picture - and may never have - of how everything works together," says Dr Tinny Ho. HORMONE REJUVENATION THERAPY What it does Claims to bring hormone levels back to the level of the patient's early 20s, and therefore reverse ageing. Be warned "We don't know enough about how these may have an impact on the different body systems in the long run," says Ho. The therapy is typically used only for people medically diagnosed with endocrine disease.