No-Poo Hair Care ยท Comparison

Water only, co-wash, baking soda or vinegar: how they compare

Water only, conditioner-only washing, baking soda and vinegar rinses are the four methods people use instead of shampoo. This guide sets out pH and irritation risk for each.

General information, not medical advice. We are not doctors and we have not tested any product. For an itchy, flaking, sore or red scalp, or hair that is thinning or changing, see a board-certified dermatologist.
Short answer. In the sources we read, water only and co-washing are the mildest, and neither cleans as well as shampoo. Baking soda is the one to avoid: a dermatology review gives it a pH of 9 and calls it "a known alkaline irritant". Vinegar is acidic and the same review says it needs diluting. None of the four has been tested in a trial.

The four methods

MethodWhat the sources sayMain risk they name
Water onlyHealthline: the cheapest and chemical-free, but hair may not feel as clean. Tap water is not neutral: Lambers et al. measured that European tap water, with a pH around 8.0, raised forearm skin pH for up to 6 hours before it returned to its usual value.May not remove oil or styling product. The pH effect was measured on skin, not the scalp.
Co-wash (conditioner only)The Cutis review says co-washing "is not harmful to the hair" but is "inappropriate" as a replacement for shampooing, because conditioners are made to add substances, not to remove dirt and buildup. Healthline: less likely to disrupt scalp pH, but may weigh hair down.Buildup. The review says conditioning cleansers are not adequate for people who wash infrequently or use styling products.
Baking sodaCutis review: pH 9; it causes the cuticle layer to open and is "a known alkaline irritant"; it lowers elasticity and increases friction, cuticle damage and breakage. Healthline: abrasive; repeated use causes dryness. The maker, Arm & Hammer, states baking soda has a pH of 8.Dryness, irritation, breakage.
Vinegar rinseCutis review: apple cider vinegar has a pH from 3.1 to 5; undiluted it may be too caustic for the hair and can irritate eyes and inflamed skin; on processed or chemically damaged hair it may increase fragility. Penn State Extension: store-bought vinegar is standardized to at least 5% acetic acid, about pH 3.Irritation if too strong. Fragility on damaged hair.

The baking soda figure differs by source: the maker says 8, the Cutis review and Healthline say 9. Both are above neutral, and the chart shows the range.

Chart of pH values: hair fiber 3.67, skin surface 4.7 to 5.1, scalp 4.5 to 6.2 in teal; store-bought vinegar about 3, apple cider vinegar 3.1 to 5, baking soda 8 to 9, European tap water about 8 in amber
pH of the body versus what people apply. Source: Cutis 2018 review; Lambers et al. 2006; Penn State Extension (2026); Arm & Hammer. Sources differ on exact values.

Does a vinegar rinse irritate? One related study

Luu et al. (2019) had 22 people (11 with atopic dermatitis, 11 healthy) soak forearms for 10 minutes a day for 14 days, one arm in dilute apple cider vinegar (0.5% acetic acid) and one in water. The vinegar did not improve skin barrier measures, and 16 of 22 (72.7%) reported mild side effects that improved after stopping. This was forearm skin, not scalp, in a pilot with 22 people. It says nothing certain about a rinse on your head, but it shows that even dilute vinegar irritated most of those people.

Why pH comes up at all

Gavazzoni Dias et al. (2014) write that alkaline pH may increase the negative electrical charge of the hair fiber surface and so increase friction between fibers, which may lead to cuticle damage and breakage. They also say there is no standardized final pH for shampoo and that studies are needed to establish the best pH range for scalp and hair. The pH argument is reasonable, but nobody has shown how much any of it matters for ordinary hair.

What the sources do not say

The honest simpler option

The mildest option in the table costs nothing: a thorough water rinse between ordinary shampoo days. If you try a vinegar rinse anyway, the review's point is dilution, and the skin study's point is that even a weak solution irritated most people. Skip baking soda. For a first month that avoids all of this, see the first-month plan.

Sources

All read on 2026-10-20. Pages and abstracts can change, so check the date shown.

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Related searches on eBay

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Applicator or rinse bottleHandy for diluting and applying a rinse the same way each time. Look for measuring marks and a cap that seals.View on eBay → pH test stripsA rough reading of a rinse or a dissolved bar. Strips are approximate, so treat the number as a guide, not a lab result.View on eBay →

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