There are many factors that may contribute to scalp inflammation. For example, according to McNeil Consumer Products in Canada, scientists have also confirmed that dandruff and other forms of dermatitis conditions can be caused by a microscopic fungus called Pityrosporum Ovale. It is known that this fungus can cause a mild infection at the roots of the hair and cause itch and flakes. Please note that scalp inflammation can happen even if you are not using Rogaine or topical minoxidil. In fact, there is no scientific study which shows that topical minoxidil is the cause of scalp inflammation.
Some people are simply more prone to certain scalp conditions than others.
Besides topical minoxidil, Retin-A is also known to be associated with scalp inflammation. Specifically, scalp treated with Retin-A will become vulnerable to sunlight and may develop an inflammatory reactions due to sun's exposure. In addition, some suggested that inflammation may be related to bacterial activity on the scalp. Researchers Young et al. proposed that inflammation is a direct cause of bacteria that inhibits in the hair follicles. Other causes of scalp inflammation are long term use of hair dyes, anti-frizz and various hair styling products that has a high alcohol content.