No, applying Garnier hair colorant to hair previously exposed to Henna or metal-salt hair treatment is not recommended.
According to Garnier's guidance:
- Hair colourant: can I apply on hair having previously used Henna or colouring products with metal salts? No, applying Garnier hair colorant to hair previously exposed to Henna or metal-salt hair treatment is not recommended.
Why is Mixing Henna and Chemical Hair Color Not Recommended?
While the reference specifically states the recommendation against using Garnier color after henna or metal salts without detailing the why, it's widely known within hair care that applying chemical dyes over traditional henna (especially those potentially mixed with metallic salts) can lead to unpredictable and sometimes undesirable results.
Here's why this caution exists:
- Unpredictable Color Results: Henna coats the hair shaft, and this coating can prevent chemical dyes from penetrating properly. The resulting color might be uneven, different from the shade on the box, or not take at all.
- Potential Chemical Reactions: Some henna products, particularly 'compound hennas' or cheaper versions, can contain metallic salts (like copper, lead, or iron). When these salts interact with the chemicals in permanent hair dyes (like hydrogen peroxide), they can cause adverse reactions.
- Hair Damage: These reactions can range from making the hair feel gummy or brittle to causing significant damage, breakage, or even a chemical burning sensation.
- Difficulty in Future Coloring/Treatments: Henna is very difficult to remove. Even after using chemical color over it, future attempts to lighten or significantly change your hair color can be challenging and potentially damaging.
What Should You Do If You Have Henna in Your Hair?
If you have used henna on your hair, the safest approach before using a chemical dye like Garnier is to wait until the henna has grown out or been cut off.
Consider these points:
- Identify the Type of Henna: Were you sure it was 100% pure henna, or could it have contained metallic salts or other additives? Pure henna is less risky than compound hennas but still affects how chemical dye reacts.
- Perform a Strand Test: If you absolutely must color your hair, perform a strand test on a small, hidden section of hair first. This is crucial to see how the color will turn out and if there's any adverse reaction.
- Consult a Professional: A professional hairdresser experienced with henna-treated hair can provide advice or potentially offer alternative coloring solutions or treatments that are safer to use over henna.
- Wait for Growth: The safest method is to allow the henna to grow out and cut off the treated sections before applying chemical color.
Mixing traditional henna and chemical hair color is generally discouraged due to potential complications. Following the specific recommendation from Garnier to avoid applying their colorants over henna is the safest course of action for your hair's health and the desired color result.
