Shampoo types and how to choose

Key takeaways

• Shampoo "types" are marketing categories built from the same few parts: a primary cleanser, secondary surfactants, conditioning agents and optional actives. A shampoo's strength and mildness depend on the whole blend, not a single label word (see how shampoo works).
• The most important choice is whether you have a scalp problem. For flakes and itch, use an anti-dandruff shampoo with a proven active (ketoconazole, zinc pyrithione, selenium sulfide, piroctone olamine). These are the only shampoo categories with strong controlled-trial evidence.
• "Sulfate-free" is not a quality grade. Sulfate-free shampoos can be mild (isethionates, glutamates, glucosides) or strong (olefin sulfonates), and sulfates mixed with amphoterics can be mild. A review of the "no sulfates, no parabens, no-poo" trend urges clinicians to answer patient concerns with facts rather than fads (Cline 2018). We found no head-to-head wear trial of sulfate versus sulfate-free shampoo on hair.
• Cleansing conditioners (co-washes) are gentle but can build up. A review describes co-washing as conditioner-based cleansing without silicones, petrolatum or mineral oil, gentle to hair but prone to leaving residue under the cuticle (Gavazzoni Dias 2019). In a double-blind trial of 200 volunteers, one cleansing conditioner was as well tolerated as three others and better tolerated than two controls (Warshaw 2020). The trial measured tolerability, not cleaning.
• Clarifying and chelating shampoos are for periodic use against styling-product buildup, hard-water minerals or swimming. See hard water and hair and citric acid.
• Bar shampoos vary hugely. Syndet bars (isethionate-based) are mild; true soap bars are alkaline (see shampoo pH).
• Apple cider vinegar and "no-poo" methods have no trial support for scalp or hair health (Cline 2018; Ogah 2025).
• Scalp scrubs have only manufacturer-linked, uncontrolled data: 29 participants, with 61% improvement in adherent flaking by day 15 (Patel 2024). Do not scrub irritated or dandruff skin, where the barrier is already weak (Harding 2002).

The main categories

2-in-1 and silicone shampoos

Anti-dandruff shampoos with conditioning silicones were designed so people do not abandon them for poor feel. A zinc pyrithione plus climbazole plus silicone formula deposited silicone smoothly on virgin and damaged hair and kept its anti-dandruff effect when users switched back (Unilever study, Turner 2013). The trade-off is possible residue on fine hair.

Low-poo, no-poo and sulfate-free

The 2018 review of the "no-poo" method frames it as a patient-driven movement and gives no outcome data (Cline 2018). Whether sulfates are inherently harmful is covered on the SLS and SLES pages: SLS is a genuine irritant in lab tests, SLES is milder, and blends differ.

What it means by hair profile

• Oily scalp, fine and straight (1A-2B), low density: a standard or lightly clarifying shampoo two to four times a week; skip heavy 2-in-1s.
• Dry, flaky or itchy scalp: an anti-dandruff active first; see dandruff.
• Wavy to coily (2C-4C): scalp cleansing needs are real but lengths are dry. Use a mild shampoo on the scalp only, about weekly for coily textures (see washing frequency), and co-wash between washes if buildup is not an issue.
• High porosity or coloured hair: milder surfactants and acidic conditioning (see shampoo pH).
• Hard-water areas: an occasional chelating shampoo.
• Thinning hair: any gentle shampoo that does not irritate the scalp; ketoconazole is an optional add-on.

Myths and facts

• Myth: sulfates damage hair. Fact: anionics extract more hair lipid than non-ionics in lab tests (Shaw 1979), but washing frequency and conditioning dominate real-world outcomes.
• Myth: sulfate-free shampoos clean poorly. Fact: some clean strongly, such as olefin sulfonates.
• Myth: co-washing is shampoo-free cleaning. Fact: it cleans little and can build up residue.
• Myth: an apple cider vinegar rinse balances scalp pH. Fact: there are no trial data.
• Myth: scrubbing removes scalp "toxins". Fact: there are no data.

Bottom line

Pick the category by scalp problem first and hair type second. Use one anti-dandruff shampoo on the scalp if you have flakes, and a plain mild shampoo otherwise. Use a clarifying or chelating shampoo only every few weeks. Co-wash only if your hair is very dry and you also shampoo regularly. Patch-test any new "natural" product if your scalp is sensitive.