Semi-permanent and temporary hair colours penetrate your hair’s cuticle (protective outer layer) to gain access to the cortex (inner layer) where your hair’s pigment is contained. Therefore, they can cause moisture loss from your hair, and subsequent dryness.
Semi-permanent dyes last for about 6 weeks and tend to fade progressively. They do not contain bleaching agents — therefore, they cannot lighten your pre-existing shade.
Advantages of Semi-Permanent Colours
- They tend to give you a more natural colour than wash-out (or 'veg') dyes, which simply rest on top of your hair’s cuticle
- You can use semi-permanent dyes straight from the applicator, without pre-mixing them
- Temporary dyes will eventually wash out if you are unhappy with the colour
Disadvantages of Semi-Permanent Colours
- Colour fade. Temporary dyes fade with shampooing and exposure to air
- They need to be frequently reapplied, which can be drying for your hair
- Overlapping. Due to frequent overlapping, temporary dyes can leave you with darker ends and lighter roots, which looks unnatural
- They do not always give full coverage of grey hairs