Origin: Since the prehistoric times, the hazelnuts have been consumed by humans ever since prehistoric times. It is believed that Hazelnuts existence was found in the excavation sites in China over 5000 years ago. An ancient manuscript has also mentioned hazelnuts as one of China’s five sacred foods. Archaeologists have found large quantities of hazelnut shells in Mesolithic and Neolithic sites in different countries like Sweden, Denmark, and Germany. Hazelnuts have been valued since the prehistoric times. 

In ancient times, it was believed that hazel trees and their nuts had great powers and healing properties. Hazelnut trees were used in many forms to hide treasures and the branches were used to dig up holes. Ancients Romans considered Hazel nuts very auspicious and they would light hazel torches during wedding nights as a sign of fertility and for a long and happy marriage.

Since ancient times, the hazelnut has been used to cure various illnesses and ailments. Greek physicians would recommend consuming crushed hazelnuts to cure coughs and the common cold. Ground hazelnuts mixed with bear grease was used to cure baldness. 
The two major hazelnut-growing areas in the world are Turkey and Oregon of the United States. Both places have different methods of cultivation.  In Turkey, the largest hazelnut producer in the world, hazelnuts are produced in an uneven and different fashion. The hazelnut trees are grown on rocky, steep hillsides in a bunch of four or five bushes.

Whereas in Oregon, hazelnut is grown along fence rows and the hazelnuts are much smaller than the ones grown commercially today. 

Scientifically: The hazelnut is the nut of the hazel. It belongs to species of the genus Corylus, especially the nuts of the species Corylus avellana. It also is called as cobnut or filbert nut according to different species. A nut is almost spherical to oval, about 15–25 mm (0.59–0.98 in) long and 10–15 mm (0.39–0.59 in) in diameter and has an outer fibrous husk surrounding a smooth shell. Usually, the nut falls out of the husk when ripe, about 7 to 8 months after pollination. The kernel of the seed can consumed or used raw or roasted, or ground into a paste. 

Usage: Hazelnuts are used in confectioneries, bakeries to make praline, and also used in combination with chocolate for chocolate truffles and products such as Nutella and hazelnut flavored liqueur. Hazelnut oil is achieved by pressing the hazelnuts. It has a strong flavor and is used as a cooking oil. Hazelnut chocolate and coffees are very famous all across the globe. Hazelnuts are rich in protein, healthy fat, vitamin E, manganese, and numerous other essential vitamins and minerals. 

Hazelnuts have a high quantity of omega-6 and omega-9 fatty acids.
They have large amounts of antioxidants which prevent cell damage and skin aging.

Below are some DIY with Hazelnuts for smooth skin and hair:

-    Take a teaspoon of roasted ground hazelnut, add half a teaspoon of coffee and sugar to it. Add a tablespoon of coconut oil to it and combine them together. Apply this scrub on the face and gently massage the skin in circular motions. This home recipe helps in getting rid of acne. 
-    Apply a tablespoon of hazelnut oil on the hair scalp and massage. You can leave on the oil overnight. Shampoo the other day and get smooth, frizz-free hair.
-    Take 2 tablespoons of hazelnut powder and add an egg to it. Mix them thoroughly and apply on the hair. Keep this pack on for 30 minutes and then shampoo. This remedy is great for dry and damaged hair.
-    Massage a few drops of hazelnut oil bi-weekly to achieve well-moisturized skin from within.
-    Take a teaspoon of hazelnut powder and add a teaspoon of yogurt to it. Apply this paste on the face for 10 minutes. Rinse later. This helps in achieving refreshed skin.