Black Seed Oil for Hair
The importance of hair in beauty is undeniable for one and all. Hair is a significant marker of youthfulness and beauty for females, whereas for males hair is a symbol of virility and masculinity. To trace back, even in the Holy Bible, there is a mention of hair and its significance where Philistines was destroyed by Samson, who took his strength from his long, flowing mane, whose strength vanished as Delilah cut his hair. The significance of hair is not only restricted to physical appearance but also it is important for avoiding lack of confidence and maintaining professional and social status. According to the American Health Journal, approximately 40 million men and 21 million women suffer from baldness in the United States.  Therefore, caring for hair and treating all scalp related diseases are essential for both the gender.
Strengthening hair roots, avoiding scalp infection, inflammation, flakiness and head lice are important for maintaining a beautiful hair and avoid baldness. History already disclosed that black seed oil was the secret of gorgeous, long locks of Cleopatra.  Queen also used black seed oil for maintaining luster to her hair and nail.  Black seed oil has several health beneficial properties, which also assist in maintaining hair health.
How black seed oil works on hair?
Thymoquinone (TQ) is the primary ingredient of black seed oil which has the anti-oxidant and anti-inflammatory effects. In addition, black seed oil also has an antimicrobial effect, so the combinations of these beneficial effects are helpful for hair growth, and it prevents scalp diseases and infections. Antioxidant and anti-inflammatory effects of black seed can inhibit cyclooxygenase and prostaglandin D2, which act as a pro-inflammatory mediators and influence inflammation. Black seed oil gives a soothing effect on the scalp in case of flakiness by preventing inflammation. Anti-oxidant effect of black seed oil assist in restoring hair follicle strength and promote hair growth. Anti-microbial effect of black seed oil prevent several viral or fungal infection on the scalp and also effective against head lice growth. [2,3,4]
Black seed oil is a natural source of essential fatty acids and amino acids, which have a preventive action against scalp dryness and skin diseases like psoriasis dandruff, responsible for hair damage. 
According to the test conducted by western researchers stated that the application of black seed oil on the scalp can prevent baldness, as it acts as a catalyst for replenishing the hair follicles and preventing baldness. 
A double-blind, placebo-controlled and randomized clinical trial conducted on the black seed oil in twenty patients with Telogen effluvium (TE). TE is a scalp disorder causes thinning or shedding of hair. In this study, the experimental group was treated with a scalp lotion containing 0.5% black seed oil daily for 3 months and follow-up continued for six months. The study result showed 70 percent patients in experimental group got improvement by a significant increase in hair density and hair thickness. The study researchers concluded that black seed oil has the potency to treat Telogen effluvium (TE). 
Another clinical study conducted on 90 patients to evaluate the efficacy of natural ingredients against hair fall control showed that hair oil constituted of black seed oil had reduced hair fall up to 76% within 15 days of the start of the application. 
One of the black seed oil users stated that after occasional applying of black seed oil on the scalp, where the hairs become thin or grayed, she got an amazing positive result. With only half bottle of black seed oil with occasional applications, she noticed thickening of hairs around the hairline and darkening of the gray/white hairs.  However it is always suggested that regular application with following proper direction for application provides a more effective result.
Direction for Application
For hair loss:
Apply black seed oil on the dry scalp after shampooed hair and leave it for certain period for oil absorption into the hair follicles. It is also recommended that one teaspoon of black seed ingestion is also helpful to maintain the overall health and even secondarily supports maintaining of the hair growth. Good hair quality is considered as an indicator of a healthy body and vice versa. 
For gray hair:
Regularly massage with black seed oil on the area of the scalp where the hair become gray to prevent graying hair. 
Directly apply black seed oil on the bald spots and keep it for certain period (almost 30 minutes) and then rinse with cold water. 
This detail illustration can explain the hair benefits of black seeds and also provide a scope for future addition of black seed oil as an active ingredient in hair care products.
- Sanusi Umar. Hair Loss Info. Published on 07-04-2012. Online available at https://www.dermhairclinic.com/hair-loss-info/
- Sierra Bright. 9 Reasons To Have A Teaspoon Of Black Cumin Oil Every Day. Published on August 30, 2016. Online available at http://www.naturallivingideas.com/black-cumin-oil-benefits/
- Deena AS Hussain, M. Musharraf Hussain. Nigella sativa (black seed) is an effective herbal remedy for every disease except death – a Prophetic statement which modern scientists confirm unanimously: A review. Advancement in Medicinal Plant Research Vol. 4(2), pp. 27-57, April 2016 ISSN: 2354-2152 Review. Online available at http://www.netjournals.org/pdf/AMPR/2016/2/16-008.pdf
- Sudhir SP, Deshmukh VO, and Verma HN: Nigella Sativa Seed, a Novel Beauty Care Ingredient: A Review. Int J Pharm Sci Res 2016; 7(8): 3185-96.doi: 10.13040/IJPSR.0975-8232.7(8).3185-96. Online available at http://ijpsr.com/bft-article/nigella-sativa-seed-a-novel-beauty-care-ingredient-a-review/?view=fulltext
- Krista Hillis. Fix Hair Loss With Black Seed Oil. Online available at http://www.thealternativedaily.com/black-seed-oil-for-hair-loss/
- Sanusi Umar. Nigella Sativa Oil Potential Usefulness in Hair Loss. Published on November 13, 2014. Online available at https://www.dermhairclinic.com/nigella-sativa-hair-loss/
- Rossi, L. Priolo, A. Iorio, E. Vescarelli, M. Gerardi, D. Campo, D. Nunno, S. Ceccarelli, S. Calvieri, A. Angeloni and C. Marchese, “Evaluation of a Therapeutic Alternative for Telogen Effluvium: A Pilot Study,” Journal of Cosmetics, Dermatological Sciences and Applications, Vol. 3 No. 3A, 2013, pp. 9-16. doi: 10.4236/jcdsa.2013.33A1002. Online available at http://www.scirp.org/journal/PaperInformation.aspx?paperID=35882
- Shahinoor Rahaman Dulal, Hasib Sheikh, Mohammad Abu Taher , Mohammad Sayeed Ur Rahaman, Zakia Rahman and M.A. Malek , Formulation and finding out the efficacy of the herbal hair oil over simple coconut oil (Purified) – A formulation and clinical study in Bangladesh, International Journal of Pharmaceutical Sciences and Research , 2014; Vol. 5(5): 1801-1805. ISSN: 0975-8232; P-ISSN: 2320-5148. Online available at http://ijpsr.com/bft-article/nigella-sativa-seed-a-novel-beauty-care-ingredient-a-review/?view=fulltext
- BkCreative. Amazing Black Seed Oil: Does it Cure Everything But Death and Make Your Hair Grow? Published on November 25, 2016. Online available at https://caloriebee.com/nutrition/Amazing-Black-Seed-Oil-Does-it-Cure-Everything-But-Death-and-Make-Your-Hair-Grow