Low-grade contact dermatitis from cosmetics is one of the most underdiagnosed conditions in women over 40. The symptoms don't look like a typical allergic reaction — no dramatic rash or swelling. Instead: persistent dryness that no moisturiser fixes. A slight roughness. Occasional redness that comes and goes.
The culprits are usually preservatives (methylisothiazolinone, formaldehyde releasers), fragrance compounds (up to 200 individual chemicals under a single label listing), and certain dyes. Your skin tolerated these at 25 because your barrier was strong enough. After 40, that tolerance drops.
Switching to a hypoallergenic, fragrance-free foundation is one of the single biggest improvements dermatologists see. Within two weeks, the persistent dryness often resolves. The texture improves. The redness fades. It looks like a skincare miracle, but it's actually just removing the thing that was causing the problem.