Hair fibre irritation - what ingredients could be causing this?

It sounds like you're experiencing a scalp reaction that could be linked to one or more ingredients in the hair fibers, powder concealers, or eyeliners you're using to conceal the scar. Even products labeled as organic or hypoallergenic can contain ingredients that might irritate sensitive skin, especially if you're using them over a long period or applying them frequently. Some common culprits that could be causing the irritation and itching include:
Preservatives: Even hypoallergenic products sometimes contain preservatives like parabens, which can cause allergic reactions or irritation for some individuals.
Dyes or Colorants: Hair fibers and concealers often contain synthetic or natural dyes, and these can sometimes trigger contact dermatitis, leading to itching, burning, or even hair shedding.
Fragrance: Some concealing products include fragrances, which can irritate the scalp, even if they’re marketed as mild or hypoallergenic.
Alcohol: Ingredients like alcohol can dry out the scalp and cause irritation or exacerbate underlying scalp conditions.
If you've used these products before without issue but are now experiencing symptoms, it’s possible that a cumulative effect is building up, or that your scalp has developed sensitivity over time. Taking a break from these products and switching to gentler, fragrance-free options could help ease the irritation. You might also want to patch test any new products before applying them to larger areas.