After dyeing your hair, it's generally recommended to wait at least 48 to 72 hours before washing it. This waiting period allows the hair color to fully set and ensures better color retention.

Here's why:

1. Color Fading Prevention: When you dye your hair, the cuticles open to absorb the color molecules. Washing your hair too soon can cause these cuticles to close incompletely, allowing the color to rinse out more easily, resulting in fading.
2. Chemical Processing: Dyeing involves chemical processes that can temporarily weaken the hair structure. Allowing a couple of days without washing gives your hair time to recover from the chemical treatment.
3. Longevity of Results: Waiting a few days helps the color bond more securely to the hair strands, ensuring longer-lasting results.

However, this advice can vary depending on the type of hair dye used and the specific instructions provided by the manufacturer. Some semi-permanent or demi-permanent dyes may suggest different timelines. Additionally, if you experience severe scalp irritation or itching, you should consult a professional stylist or healthcare provider.

In the meantime, you can use a dry shampoo to refresh your scalp and roots if needed during this waiting period. Also, when you do start washing your hair again, use a color-safe shampoo and conditioner to maintain your new hue.