The draw of shampoos that promise to boost hair growth is pretty clear. Someone who wants to encourage hair growthwill like the sound of getting the benefit from a product that's a hygiene staple.

The question of how effective the shampoos are isn't as obvious, though, and comparing all the available options with various ingredient highlights can easily become a time suck. Before you start browsing, read a summary of how to find the best shampoo for hair growth from Wendy Roberts, M.D., F.A.A.D., a Rancho Mirage, California-based dermatologist.

A: To find the best shampoo for hair growth, your main priority should be choosing a suitable formula for your scalp type, according to Dr. Roberts. Certain shampoo ingredients may help promote healthy hair by boosting circulation, she says.

If you're after a formula that'll promote healthy hair growth, follow these steps when selecting your shampoo.

A healthy scalp is an ideal environment for hair growth, so it's key to find a shampoo formula that's suited to you individual needs, according to Dr. Roberts. Think about whether you have a dry scalp, with hair that can feel brittle and stiff, or a more oily scalp that becomes shiny a day or two after you wash it. Then, choose a corresponding shampoo for dry or oily hair, she suggests.

Choose poorly, and you could impede your hair growth. "An example of this would be, someone with very dry hair — typically [Black people] have dry hair," says Dr. Roberts. "So if you were to use a really drying, harsh alcohol-based shampoo on that hair type, it's going to make [the hair] break, and that would contribute to hair loss."

The other side of the coin is that if you have a scalp that produces a lot of oil, you want to avoid products that are rich in conditioning ingredients such as shea butter, coconut oil, or silicones, which can make your hair appear limp, according to Dr. Roberts. Build-up from excess oil and hair products can negatively impact hair growth, as Shape previously reported. "If your follicles aren't clean, then the hair might face impedance as it grows out of the follicle," says Dr. Roberts.

Some scalp conditions, such as severe psoriasis, require special shampoos, notes Dr. Roberts. When in doubt, check with a dermatologist who can help you find the right shampoo and overall treatment plan.

When seeking out the best shampoo for hair growth, you can also look out for certain promising ingredients. Just keep in mind that even the best hair growth shampoo won't produce miracles. "The ingredients are somewhat helpful, but the fact is that shampoo sits on your hair for such a short amount of time that these ingredients can't even get through to your scalp or your hair," says Dr. Roberts. "There's not enough time, they're rinsed off. And the skin on the scalp is very thick."

One ingredient that deserves your attention is the star of everyone's favorite morning beverage. "Caffeine may actually have some effect because it can increase circulation," says Dr. Roberts. "Caffeine makes your blood vessels dilate, increasing blood flow," which boosts the delivery of oxygen and nutrients to hair follicles, which can, in turn, boost hair growth, she says.

While it's also a popular ingredient in shampoos that promise to fight hair loss, biotin probably won't produce hair growth effects when used topically, according to Dr. Roberts. "Biotin is not penetrating your scalp," she says. "That's a myth around biotin. It's really not doing anything except when you ingest it. Biotin's great for hair, but that's ingestible biotin."

As for keratin, the ingredient can condition hair to make it appear fuller — just know that it won't actually impact hair growth, according to Dr. Roberts. She likens keratin's effects to applying makeup vs. using skin-care products. "It forms a coating, but it's not going to like get into your hair and help with hair growth," she says. "It can lay on top of your hair and make it seem thicker."

You don't want to focus all your energy on choosing the best shampoo for hair growth. Instead, you should also tailor your hair washing routine to promote a healthy scalp. When applying the shampoo, give yourself a scalp massage, recommends Dr. Roberts. "Massage is very important during shampooing because it helps the product penetrate and helps with circulation."

For healthy hair growth, it's important to strike a balance between washing your hair too frequently and not often enough. Washing too frequently can present a different issue if you're experiencing hair loss, according to Dr. Roberts. "If you're having a hair shedding problem, you don't want to over-wash your hair, because every time you manipulate your hair, you're going to lose hairs," she says. "Normal shampooing of your hair should not cause a lot of hair to pull out, but if you're having hair shedding problems for X, Y, Z reason,you don't want to shampoo too often." (FYI, hair loss can result from genetics, stress, and endocrine disorders, among other causes.) Here's a guide to how often to wash your hair, depending on your hair type.

On the other hand, not washing your hair enough can lead to growth-inhibiting build-up. It's key to wash your hair frequently enough with a suitable shampoo, and you can also use products between washes that incorporate exfoliating ingredients (e.g., salicylic acid, lactic acid, or an enzyme) to keep your scalp clean, says Dr. Roberts.

One important thing to note: A slew of factors can affect your hair growth, from your genetics to your diet. If all the factors were actors in a play, the shampoo you use would have a minor role — think: third group to take their bows — but a role nonetheless, says Dr. Roberts. So while it can be helpful to find the right formula, you don't want to neglect the bigger picture if you're trying to tackle hair loss or thinning.