Salicylic acid comes in handy when it comes from everything from zapping acne to getting rid of warts. To boot, it can help get rid of your dandruff. Salicylic acid has a keratolytic effect on the scalp, which helps loosen and dislodge the skin scales we all know as dandruff. You can make an at-home sal-acid shampoo by adding two crushed uncoated aspirin to your regular shampoo. Aspirin contains salicylates, the same active ingredient in medicated shampoos containing salicylic acid.

Or you can simply buy a dandruff shampoo that contains 0.5 percent salicylic acid, such as Neutrogena T/Sal Therapeutic Shampoo Scalp Build-Up Control, $7.14. Many medicated dandruff shampoos with salicylic acid also contain sulfur for a one-two punch against dandruff, including Jason Dandruff Relief Treatment Shampoo, $12.77. No matter whether you're going the DIY or store-bought route, be sure to follow with conditioner, as salicylic acid can dry out your hair and scalp.

Zinc pyrithione is the workhorse of anti-dandruff ingredients. This zinc compound inhibits the growth of fungus and bacteria, stopping two major causes of dandruff in their tracks. You can find this standout ingredient in L'Occitane Aromachologie Anti-Dandruff Shampoo, $22, which also includes five essential oils known for their revitalizing properties: mint, thyme, grapefruit, cedar and lavender.

Selenium sulfide will help knock out the excess scalp fungus (yes, gross), which can cause dandruff. This both soothes irritation and slows the rate of skin cell shedding. You'll see it in 1 percent or 2.5 percent concentrations in anti-dandruff shampoos. Look for it in Head & Shoulders Clinical Strength Shampoo, $7.99, which promises to remove 100 percent of flakes and relieve itchiness. But one warning: This ingredient has been known to discolor blonde, gray and dyed hair, so only use as instructed, and be sure to rinse well after shampooing.

Um, tar in our hair? Normally, we'd take a hard pass, but hear us out. Coal tar, a byproduct of the coal manufacturing process, doesn't sound pretty but it can attack dandruff caused by seborrheic dermatitis, eczema and psoriasis. This ingredient slows down the rate your skin cells turnover, which makes your scalp less likely to flake. Seek out products that contain 5 percent coal tar, such as PsoriaTrax Anti-Dandruff Tar Shampoo, $18.95.

When you're faced with stubborn dandruff that just refuses to go away with other dandruff shampoos, it's time to call on ketoconazole, the king of scalp antifungal agents. Ketoconazole treats a number of different types of fungal and yeast infections and is usually the ingredient used in prescription dandruff shampoos. You can find the active ingredient in OTC anti-dandruff shampoos, like Nizoral A-D Shampoo, $16.99.