BOTOX jabs may cause muscles to waste away into fat, scientists warn. Researchers have discovered that the cosmetic treatment could cause harmful side effects - even areas of the body which have not been injected. They warn that the jab - used by millions every year to banish wrinkles and plump-up lips - could cause harmful side effects when used over long periods of time. For the first time experts have found that Botox causes muscle wastage in parts of the body not injected. Canadian researchers studied the effects of the substance, known amongst in the medical profession as Botulinum toxin A, on a group of 18 rabbits over a period of up to six months. Their study, published in the Journal of Biomechanics, found that limbs which had been injected with the substance experienced muscle wastage of up to 50 per cent. But alarmingly they also discovered that muscle loss also occurred in limbs that hadnt been injected - suggesting the harmful effects of the jab could be spread to other parts of the body. The researchers, from the University of Calgary, warn that their findings 'raise important questions about the long-term use of the popular cosmetic treatment. Experts are already aware of the potentially harmful side effects of Botox such as facial sagging and muscle weakness. But until now they assumed this only affected areas which had been injected. This research suggests that women having Botox injections in their forehead could potentially experience muscle weakness or muscles turning into fat in other parts of their body. The cosmetic treatment - which costs up to 200 a time - has soared in popularity and around a million injections are carried out at private clinics every year. It is by far the most popular non-surgical procedure and the UK market is worth 18 million. Botox works by stopping the chemical reactions in muscles that make them naturally contract - effectively paralysing them. It is injected into the muscles which when contracted, cause wrinkles in the overlying skin. Once the muscle is paralysed the overlying wrinkle cannot form. Daily Mail