Hair extensions do not damage hair. The damaging aspect of hair extensions lies in the removal process, type of extensions, and hair maintenance.The popular methods of applying hair extensions are gluing, taping, weaving, cold or hot fusion and clip-ins. The healthiest and easiest method of adding extensions is through the weaving method. The hair is sold in long wefts or tracks like human hair weave. Your hair is braided and the wefts of hair are sewn on the braids. This is the safest and healthiest because there are no chemicals involved your hair is actually being protected because of the braids. As long as, the hair is maintained by always detangling it after washing and having a professional remove the wefts, weaving can be used as a protective hairstyle that promotes hair growth. Clip-ins are not damaging if you are gentle with the clip-in extensions and keep it from tangling if you remove them with care instead of yanking them out. Gluing in extensions is the quickest way to apply extensions but can damage hair only when it's being removed. During the removal process the hair needs to be saturated with a glue remover and allowed enough time for the glue to soften. The weft of hair should essentially fall off the hair while you guide it with your hands. When glued hair is removed like this and the glue is washed thoroughly your hair will not be damaged. Patience is key because if you dont wait long enough to remove the wefts of hair, that's when you start pulling and damaging your hair. The same applies to taping but taping is very hard to remove on your own and you should have someone else, preferably a hairdresser experienced in extensions remove them. Cold or hot fusion must be done by a professional and removed by a professional to ensure there is no damage done to the hair.