Reader question: How do you know if you're acidic and what base makeup to use?

During my recent trip to the mall, I was trying to find miself a good concealer. Upon asking for assistance, the first question I got from the sales rep was "Ma'am acidic po kayo?" I didn't know what to say because I really don't know if I am or I'm not, to cut it short she said I am acidic and should get a shade lighter than my color (I'm NC30). Thing is, when I went to the other stall, the sales rep told me I'm not acidic so I ended up confused and yeah, empty-handed. I wanted to find out my skin type first. Any tips on how I can find out? - Purplechef

Hey Iko! Our skin is actually naturally acidic with a pH level between 4.5 and 6.2. It is coated by what is called an acid mantle, which is crucial in protecting our skin from bacteria, fungi, and other irritants that might get into our skin. It's also what keeps our skin moisturized and healthy overall.

Natural factors like age, level of your skin's oiliness, moisture, and sweat, can affect how acidic you are. External factors like the products you use (soaps, cosmetics, lotions, etc.) can also affect your skin's pH level.

So how does this all apply to your foundation or concealer? Some of you might have noticed that your face makeup turns darker or changes color the longer you wear it. That's completely natural, as you really have to give your makeup some time to settle and adjust on your skin's surface. No base makeup ever looks 100% like it does when you first swatch it on your skin!

How dark or off it looks depends on two things, I find: the formula of the foundation and how oily/acidic your face is. If the formula sucks and if you're particularly oily then it's not going to look good. Chuck the foundation and look for another one! A good foundation should be able to work with your skin and stay cohesive for as long as you plan to wear it.

However if you're very oily/acidic then you might have to get your base makeup one shade lighter than your actual shade. This is just to give your base some leeway to properly adjust on your skin.

In my experience my face makeup changes color a tiiiiiiny bit but it's very minor so I don't mind. :) Like I said, all makeup will adjust to your skin's surface because hey you're slathering it on a living thing - it's really not going to stay the same in the natural course of your day! The key is to finding an acceptable level of adjustment. It's good to treat your neck as the reference point. If it's darker than your face then it's okay for your face makeup to darken; if it's lighter then get a slightly lighter shade than your face.

Wait, is there a way for you to find out how a foundation, powder, or concealer will adjust on your skin? Yes! Just ask the sales assistant to apply it all over your face, walk around the mall for about five hours (even longer), and check it in daylight afterwards. If the base looks alright then it's for you. If it darkens too much then just get a lighter shade. I know it sounds like a lot of work but if you're going to blow serious money on a product then a little inconvenience is worth it in the end. :)

And lastly: don't put too much faith on sales ladies. I mean, in the end, you're the only one who can decide what truly works and looks good on you. So try a product out for yourself first before committing.

So there you go, I hope this helps! I want to know: are you very acidic or are you just using the wrong foundation?