Tea tree oil
BMJ Group Medical Reference
Tea tree oil is a plant extract that's been used to treat dandruff. We haven't looked at the research on this treatment in detail yet, but one study found that a shampoo containing 5 percent tea tree oil helped with dandruff when used every day. 
Because we haven't looked in detail at the research on this treatment, we can't say whether it causes side effects, or how common they might be. Some people have had problems such as skin irritation or an allergic reaction when using this treatment. 
There have been rare reports of boys who haven't yet gone through puberty starting to grow breasts while using products containing tea tree oil and lavender oil.  But there have been so few cases, it's impossible to say whether these products really caused the problem.
Tea tree oil can irritate your eyes, so be careful when using the shampoo. Rinse with plenty of water if you do get it in your eyes.
For references related to Dermatitis click here