How many times have you purchased a hair product that sounds like it will work miracles, only to have your hair look more like Snape’s from Harry Potter? Or, how many times have you had a friend rave about a product, only for it to fall flat on your mane?

1. Scalp

Many people forget to pay attention to their scalp and solely look at their hair, but you need to start from the top and work your way down. Your scalp produces natural oils that contribute to hair health, as this is where hair grows from. Sebum production affects how oily your scalp is. If you have an excess, your hair will get greasier faster. If you don’t produce enough sebum, your scalp will be dry.

How do you determine sebum production? Examine your scalp one day after washing your hair. Is it greasy? If yes, then you have an oily scalp. If it looks relatively unchanged, you have a normal scalp. You have a dry scalp if you notice any flaking or dandruff.

If you have a dry scalp, you'll want a shampoo and conditioner that restore or hydrate it. If you have an oily scalp, be sure to apply your products mid-shaft to ends and avoid the roots.

2. Diameter

After determining the condition of your scalp, you need to figure out the diameter (or width) of your hair. Keep in mind, this is not to get confused with how much hair you have, but it is looking at an individual strand. Is it fine, thick, or somewhere in between?

Take a single strand of your hair and rub it between your fingers. If you can barely feel it, or not even feel it at all, you have fine hair. If it feels strong or thick and textured, your hair is coarse. If your hair lies somewhere in the middle, it is likely medium in diameter.

3. Density 

When talking about density, we’re talking about how much hair you actually have. Just because someone has “fine hair”, doesn’t mean they have “thin hair.” You can have fine hair, but have a lot of it, giving a thicker appearance. You can also have thick hair, but not have much of it, giving hair a thinner appearance. The diameter of your hair does not determine the density.

To figure out how “dense” your hair is, take a section of hair from the front side of your head and pull it out to the side. How much of your scalp can you see? If you can see sections of your scalp poking through, or if your scalp is visible underneath, you have thin hair. If you can barely see your scalp at all, your hair is thick. Again, if it is somewhere in between, it is medium.

4. Porosity

The porosity of your hair refers to the ability of your hair to absorb moisture. The more porous the hair, the more raised the cuticle is. This will help you determine how much damage you have. 

If you have highly porous hair, it means the protective layer, or cuticle, of your hair has been badly damaged and is raised. Hair that is brittle, dry, and/or prone to breakage usually has a higher porosity. While your hair soaks up all the product it can get, it does not retain what it absorbs. Because the cuticle is so raised, it cannot close and keep that moisture in. So, your hair likely dries faster, but does not feel soft, strong, or hydrated at all. Be careful not to damage it further through heat styling or chemical services. Try using a hydrating shampoo and conditioner, along with deep conditioning treatments to repair the hair. 

If your hair has a low porosity, the cuticle is flat, so product tends to sit on top of the hair, rather than get absorbed. Hair that has a lot of bounce or elasticity, or takes a long time to dry usually has a very low porosity. Because product isn’t absorbed, it tends to build up on the hair and scalp, so remember; less is more. Be sure to distribute product evenly to damp hair to avoid build-up as well. Also, because your hair has minimal damage, avoid "heavier" shampoos and conditioners that are aimed at repairing the hair; it doesn't need it!