Hair dye shampoos (sometimes called colour-depositing or "3-in-1" dye shampoos) are an easy way to cover gray at home. But they are still hair dye. Many contain the same colour chemicals as boxed permanent dye, including para-phenylenediamine (PPD) or related ingredients. This guide covers what to check and how to patch test. It is general information, not medical advice.
Is hair dye shampoo safe?
For most people, a dye shampoo used as directed causes no problems. However, allergic reactions to hair dye are fairly common and are usually mild: itching, redness or burning on the scalp, ears or neck. Severe reactions are rare but possible. According to the NHS and dermatology sources, PPD is the ingredient most often responsible.
How to do a 48-hour patch test
- Read the leaflet in the pack and follow its specific instructions.
- Mix a small amount, or use the product as the pack directs, and dab it on a small patch of skin behind your ear or inside your elbow.
- Let it dry and leave it uncovered and unwashed for 48 hours.
- If you notice itching, redness, swelling, burning or blisters, do not use the product. Wash the area and seek medical advice if the reaction is strong.
- Repeat the test every time, even with a product you have used before, because allergies can develop over time.
A negative patch test lowers the risk but does not guarantee you won't react.
Label checklist
- Look for "Contains phenylenediamines" or PPD, PTD (toluene-2,5-diamine) or p-aminophenol in the ingredients.
- "PPD-free" doesn't mean allergy-free. A recent study of hair dyes sold in the US found some products labelled PPD-free still contained it.
- "Plant" or "natural" on the box does not guarantee the product contains no synthetic dyes.
Do not use hair dye shampoo if
- You have reacted to hair dye before.
- You have had a black henna tattoo, which raises PPD sensitisation risk.
- Your scalp is broken, sunburnt or irritated.
- You are under 16.
- You are pregnant or breastfeeding and have not checked with your doctor.
Using it safely
- Wear the gloves supplied.
- Keep it away from your eyes, eyebrows and eyelashes.
- Do not leave it on longer than the pack says.
- Rinse thoroughly.
FAQ
Does dye shampoo cover gray completely?
Results vary with your hair colour, the amount of gray and how long you leave it on. Light-to-moderate gray usually blends best. Do a strand test first.
Is it safe during pregnancy?
Ask your doctor or midwife before using any hair dye.
We stock Nova hair dye shampoo in our hair care collection. Please patch test before every use.
Sources: NHS "Hair dye reactions"; DermNet "Paraphenylenediamine and hair dye contact allergy"; "Contact Allergens in PPD-Free Hair Dyes" (PMC).