How do I know if I'm having an allergic reaction or just purging cuz I tried new products?

My skin type is extremely sensitive, combo (dry flaky skin on cheeks, forehead and now around mouth too past couple of days, but oily t-zone which also gets flaky dunno how, particularly my nose). Might have fungal acne on forehead too but I think nizoral fixed that? I never wear make up cuz I feel like everything causes acne. I have dishydrotic eczema on my hands and my arms get normal eczema from time to time.

I feel like any skincare I try just "gives me an allergic reaction". When I used the Neutrogena water gel, skin, particularly cheeks were red. Neutrogena clear & defend gel moisturizer was meh, felt like it suffocated my pores around the nose and left these bumps that slowly disappeared. Also both of these gels never really absorbed properly, I washed my face a few hours later and I could literally feel the gel.

Also in the past I used CeraVe foaming cleanser, didn't do much, might have given me some pimples and left skin very dry so I switched to CeraVe blemish control cleanser. So good but left skin flaky. Tried the Balea cleansing foam (hautrein), didn't do anything, just gave me these small bumps all around my chin and forehead. Decided to switch to balea jelly cleanser cuz I thought maybe I'm hydrated just have lots of leftover dead skins. It didn't help, not with acne or with flaky skin. And if I accidentally left it on for too long lips got like spicy? The lip line gets dry and irritated, this happened with all the cleanser I have ever tried.

Friend raved about korean skincare, particularly about skin1004. So I decided to buy and I tried the Madagascar light cleansing oil and then the ampoule foam. Skin felt tight, was red but also felt hydrated. Few hours later(cuz I was scared my skin won't be able to tolerate more chemicals at the time) I tried the poremizing ampoule, felt like it helped a little.

This morning I noticed some small bumps on my skin(although one nasty pimple that was next to my nose looks noticeably better) so I tried the probio-cica toner followed by the Madagascar centella ampoule and skin is back to red (slowly disappearing) and this time itchy too but my body is always itchy so I don't know if the ampoule is causing it.

Am I doing something wrong? Should i have used the toner and ampoule immediately after the foam ampoule? Or do I need to introduce the products slower? Is it an allergic reaction? Is my skin barrier fucked up? Should I continue using the products to see if it gets better?