Reasons for the appearance of hard grains in the scalp
Solid grains can appear on the scalp or at the level of the hairline. This condition can be considered a complex skin disorder, but it can generally be caused by four underlying factors.
Increased secretion of fats or oils
Accumulation of dead skin cells or dirt on hair follicles
Inflammation of blocked hair follicles
Increased bacteria responsible for acne
The scalp is rich in hair follicles and sebaceous glands, so if the follicles or pores get clogged with oil or dirt, it can lead to hardened pimples. These blisters can appear even if a person takes care of the cleanliness of their scalp, but sweating, build-up of oils or dirt, or improper washing of the scalp can lead to clogged pores.
Therefore, a person should re-monitor their hair care routine, as many pimples on the scalp can be caused by shampoos, styling gels, and hair sprays that leave residue on the scalp and clog the pores.
Pimples can be stimulated by applying hair cosmetics to the scalp.
Hormones can also cause pimples on the scalp, especially testosterone, which causes an increase in oil production. The increase in this hormone during puberty can be responsible for the appearance of pimples on the scalp, and adults can also suffer from pimples for this reason.
Genes can also affect the skin, so if you have a family member with scalp acne, that makes you more likely to develop severe scalp acne.
Types of grains in the scalp
The grains on the scalp usually vary in severity and the type that appears on the scalp, and this matter can affect treatment.
Classification of pimples on the scalp according to their severity includes:
Mild scalp love
The moderate kind
Scalp blisters are painful and hard
Types of bumps that appear on the scalp can include: 
Black or white heads
These types are small bumps that a person feels when they touch their scalp. They can be white or red blisters with a black spot on top called blackheads.
Papules and pustules
Papules are raised bumps on the surface of the skin that have a rough texture in the absence of a group of them, while pustules are bumps filled with a white or yellow substance like pus.
Nodules or cysts
These nodules or cysts are among the most severe forms of scalp acne. Nodules are raised bumps that are hard to touch, while cysts have a smoother texture because they are filled with fluid.
A doctor should be consulted in the event that nodules or cysts appear, which are a type of severe acne that appears on the scalp, as a result of the risk of developing some health disorders.