Rosemary and Bicarbonate of Soda for Hair: Benefits and Risks

Mixing rosemary with bicarbonate of soda has become a home remedy used chiefly to remove oil and residue from hair. It also appears in posts claiming it can strengthen strands or darken grey hair. Rosemary contains antioxidant compounds and is studied for use in hair formulations, but there is no proven evidence that a homemade infusion works against white hairs. Bicarbonate of soda, meanwhile, cleans intensely because it is alkaline; this same property can dry out the hair shaft and irritate the scalp.

What is a rosemary and bicarbonate of soda mixture used for on hair?

The most credible effect is cleansing. Bicarbonate of soda may help lift excess oil and build-up left by styling products, while a rosemary infusion contributes fragrance and plant compounds to the mixture. As a result, some people use this combination as an occasional rinse when their hair feels weighed down.

That is not the same as saying that the remedy promotes hair growth or restores pigment to the strands. Effects linked to this home use include:

• More intensive removal of oil and surface residue;
• A feeling of a cleaner scalp;
• The distinctive scent of rosemary;
• A possible temporary reduction in the heavy appearance of the hair;
• No evidence that it reverses grey hair.

Can rosemary genuinely strengthen hair and encourage growth?

Research has examined rosemary oil and extracts in relation to hair growth, but these studies use specific preparations and concentrations. They do not show that boiling sprigs of the herb and applying the water to the scalp produces the same outcome. Some people may use an infusion as a homemade cosmetic, but persistent hair loss or the appearance of bald patches requires the underlying cause to be investigated.

Why does bicarbonate of soda need more care than rosemary?

Bicarbonate of soda is alkaline, whereas the hair and scalp naturally have a more acidic environment. Repeated application may increase friction between strands, contribute to dryness and make the cuticle feel rougher, particularly on bleached, curly, dry or chemically treated hair.

Overly harsh cleansing may also strip away lipids that help protect the hair shaft. Indications that the method is not working well include:

• Hair that feels rough or is difficult to detangle;
• A noticeable increase in frizz;
• Burning or itching of the scalp;
• Redness after application;
• Strands becoming more prone to breakage after repeated use.

Can the mixture darken grey hair?

There is no robust evidence that rosemary and bicarbonate of soda make melanocytes resume pigment production in hair that has turned white through ageing. The circulating recipe suggests boiling rosemary sprigs in water, adding bicarbonate of soda and using the cooled preparation as a rinse, but any visual change is likely to be subtle and unpredictable, rather than comparable with the effect of a hair dye.

• White hair appears chiefly because melanin production declines;
• Bicarbonate of soda does not reactivate the cells responsible for pigmentation;
• A rosemary infusion does not act as a permanent dye;
• Light-coloured hair may react differently in appearance to plant residue;
• Products formulated for colouring provide more predictable results.

Occasional use is not the same as making the mixture a routine

Anyone choosing to try a preparation containing rosemary on hair should first test it on a small area and stop using it if burning, itching or redness occurs. Bicarbonate of soda calls for even greater caution: its cleansing strength does not mean it is suitable for frequent use, and shampoos formulated for deep cleansing provide far greater control over pH and concentration.

The mixture became popular because it combines two inexpensive ingredients with an apparently straightforward explanation, but its benefits need to be viewed in the proper context. Rosemary has cosmetic and scientific interest in specific formulations, while bicarbonate of soda can remove residue precisely because it is alkaline. The same mechanism that leaves hair feeling clean also explains why overuse may result in dryness, frizz and irritation rather than stronger strands.