The avoid list

Reactive skin collects rules. Somebody swears off silicones, somebody else off every preservative, and the shelf ends up run by bans nobody remembers the reason for. A shorter list with a reason per entry works better. This is that list, plus the bans worth lifting.

The information is on the back

Fragrance goes in for two jobs: to make a product smell pleasant, and to cover the smell of its raw materials. That second job is why something that smells of nothing can still carry fragrance materials, and why the front of a box is a poor place to shop from. The back is more useful. EU rules require 26 particular fragrance allergens to be named individually once they pass 0.001 percent in a leave-on product or 0.01 percent in a rinse-off one, so limonene, linalool and their relatives clustered at the end of a list are that rule doing its job.

The list

Fragrance and essential oils. The clearest numbers come from people patch tested for a suspected contact allergy, so read them as rates inside a group that already had a problem, not rates across everyone. Within that group, cinnamal comes back positive in about 3 percent, eugenol 2.4, citral 2.1, linalool 1.3, limonene 0.8. Two of the 26 are now banned outright in the EU. Essential oils are fragrance under a nicer name, and dose matters: tea tree above 5 percent causes contact dermatitis in roughly 3 to 7 percent of users, while low percentages suit most people. Most people is doing work in that sentence. If flushing or rosacea is your problem, take the harder line the rosacea step later in this course takes: fragrance and essential oils in any amount. Those terpenes also oxidise on the shelf into stronger sensitisers than they started as, so bin anything past a year.

MI and MCI. Methylisothiazolinone and methylchloroisothiazolinone were the highest-incidence contact sensitisers of the 2010s, at about 3.5 and 2.5 percent positivity in that same group. The EU banned them from leave-on products in 2017, so a cleanser or shampoo is where they turn up now.

Denatured alcohol near the top of the list. As a trace solvent it's unremarkable. As the second or third ingredient it raises water loss and lowers hydration, and it's a documented flushing trigger in rosacea-prone skin.

Menthol, camphor and peppermint. Menthol switches on TRPM8, your cold receptor, so the cooling you feel is a receptor being triggered rather than a temperature dropping. The same vasoreactivity makes it a poor idea on flush-prone skin, and camphor adds sensitising potential on top. Witch hazel, eucalyptus and methyl salicylate belong here too.

High-percentage acids and physical scrubs while you're reactive. Not forever, and not every acid. While the barrier is open, strong AHAs, rotating brushes and gritty scrubs keep reopening what you're trying to close. Azelaic acid is the exception the later step in this course makes the case for: it's one of the few actives dermatologists tend to keep running during repair.

What's fine, despite the reputation

Cetearyl alcohol and its relatives are waxes rather than the drying kind of alcohol; in a UK audit of 3062 consecutive dermatitis patients only 0.8 percent tested positive. Phenoxyethanol has a low contact-allergy rate next to the isothiazolinones and is capped at 1 percent in the EU; seeing it mostly tells you a water-based product is properly preserved.

Silicones earn their ban the least of anything on anyone's list. Dimethicone isn't absorbed through skin, sensitised nobody in human repeat-patch testing at 5 percent, and suits sensitive and flush-prone skin precisely because the film it forms is inert. Skip it on environmental grounds if you like; there's no skin argument.

Niacinamide is the other rescue. Clinical studies use 2 to 5 percent, and on flush-prone skin aim at the top of that band, 4 to 5, where the rosacea step puts the sweet spot. The 10 to 20 percent serums trending online are why people think niacinamide is bad for rosacea.

Centella triggers allergy in a small number of people, though testing classes it a very weak trigger, low risk even on broken skin; patch test it if you've reacted to botanicals before. Panthenol, allantoin and colloidal oatmeal carry very low allergen risk and are the backbone of most calm-down routines.

The move that beats the list

Stop fighting ingredient by ingredient. Twelve ingredients gives you twelve suspects; thirty-five gives you thirty-five, and you'll never finish the investigation. Buying short lists does more for reactive skin than memorising any avoid list, including this one.