An oily scalp is caused by the hyperactivity of the sebaceous glands of the scalp. Oil would be a misnomer because the substance is actually called sebum and consist of wax monoesters, triglycerides, and fatty acids but they largely follow the properties of oil itself. The sebaceous glands are glands that exist in the mucosal layer of the skin and are half way at the base of each hair follicle. The sebum that is secreted is exuded from the hair shaft. The reason that there is a certain amount of odor is because of the appocrine sweat glands that also exude from the hair shafts. Theses glands secrete a substance that bacteria immediately act upon thereby releasing odorous gases. Treating this condition just requires more hair washing and using a disinfectant.
The best method for treating an oily scalp is to shampoo. Most shampoos have detergents in them that will completely rid the scalp of any oil; however, the problem with this approach is that you end up causing excess sebum to be secreted and the problem increases further. What is really required is for the scalp to be rid of microorganisms and a bit of deodorizing. One of the best shampoos that you can use in this regard is an anti-dandruff shampoo. Most of the more prominent brands of anti-dandruff shampoo contain the active ingredients like zinc pyrithione and selenium sulfide, which are quite effective in removing some of the odor causing microorganisms in the scalp. It is important that you instruct your husband to shampoo at least once in three days or when there is too much oil on his scalp. This is best ascertained by running a finger through the parting in the hair and checking for the amount of oil. Before shampooing, also ensure that your husband applies some salicylic acid through his hair, as this will clear away any dead skin in the hair. It also has antiseptic properties.
The other part of the remedy is applying some perfumed substance in the hair after a hair wash. This can be a hair gel or any sort of lotion for the hair. Alternatively, you could also advise him to prepare the water that he will wash his hair in by adding some rose water to it and then washing his hair. Rose water could also be substituted by his favorite cologne as well. It is also important to keep the length of hair just enough so as not to trap heat in the scalp and cause sweating.