How do I perform the sensitivity test correctly and why is it necessary every time?

Mix a pea-sized amount of color cream with an equal amount of developer (the ratio is typically 1:1 for Rubella Fashion colors, but check the leaflet in your box). Using a cotton bud, apply the mixture to a clean, dry area of skin about 1 cm² behind the ear or on the inner forearm. Leave it uncovered and do not wash the area for 48 hours.

Watch for any redness, itching, burning, swelling, blistering, or rash. Even mild irritation means you should not use the product on your scalp. Sensitivity can develop at any time — previous uneventful use does not guarantee future safety because the immune system can become sensitized with repeated exposure to oxidative dye precursors like PPD or PTD.

If you have a reactive scalp, history of contact dermatitis, or have ever reacted to a black henna tattoo, the risk is higher. In those cases, consider a patch test supervised by a dermatologist or opt for a PPD-free alternative. The test takes two days, so plan your coloring session accordingly; skipping it risks a severe allergic reaction that can spread beyond the scalp.