Why does The Ordinary Niacinamide sting?

What could be causing the sting?

• Sensitivity to niacinamide. Although generally gentle, niacinamide can occasionally cause burning, itching, redness or an allergic reaction. General guidance for sensitive skin is to start slowly with a low concentration; most niacinamide products contain 5% or less.
• An already irritated skin barrier. The barrier is the outer protective layer that helps retain moisture and keep irritants out. When damaged, skin becomes more sensitive. Retinol and glycolic acid can also irritate skin, particularly sensitive skin.
• Too many products introduced together. Several active skincare products used at once can irritate skin. Adding products individually makes it easier to work out which one causes trouble.
• A reaction to another ingredient. Skincare ingredients, including preservatives, can cause allergic contact dermatitis, an itchy, inflamed skin reaction. Stinging alone cannot identify the ingredient responsible or tell you whether the reaction is an allergy.

The Ordinary's serum contains 10% niacinamide, but that does not mean everyone who experiences stinging is reacting to the concentration. A lower concentration is an option for sensitive skin, not a reason to keep applying a formula that already causes a reaction.15

What should you do now?

1. 1Gently wash the serum off as soon as possible. The Ordinary's directions say to rinse, discontinue use and consult a doctor if irritation occurs.
2. 2Do not apply the serum again to test whether the reaction repeats. A cool compress or petroleum jelly can help relieve a product reaction.
3. 3Check whether you recently added other products. Avoid introducing several new active products together. If a prescribed product also stings, ask your dermatologist whether that is expected before stopping the prescription.
4. 4Seek medical advice for persistent, recurring or severe symptoms. See a dermatologist if the reaction is severe and does not improve with a cool compress or petroleum jelly.

Watch for itching, swelling, blisters, dryness or cracking as well as colour changes. Contact dermatitis can appear within hours or days; lighter skin can look red, while darker skin can look dark brown, purple or grey. A dermatologist can arrange medical patch testing when the trigger is difficult to identify.46

How should you test a new product?

For a new skincare product, apply the normal amount to a small spot on the underside of your arm or bend of your elbow twice daily for seven to 10 days. Leave a serum on as you normally would. If redness, itching, swelling or another reaction develops, wash it off and do not use it again. This home test helps predict a reaction; it is different from medical patch testing to identify an allergy.4

How is the serum meant to be used?

For skin that tolerates the serum, The Ordinary advises a few drops after cleansing, before oils and heavier moisturizers, morning and evening. Apply only to intact skin. For sensitive skin without a reaction, the brand suggests starting one to two days a week and increasing gradually. That starting schedule is not advice to continue through stinging.25

The Ordinary advises keeping this serum separate from direct or indirect vitamin C because combining them can reduce effectiveness. It allows pairing with hyaluronic acid, salicylic acid and retinoids.5

Sticky texture and pilling are separate application problems, not bonus skincare benefits. The Ordinary links them to excess product or incorrect layering and advises letting each layer absorb before applying the next. Using less can address those texture problems; it does not replace stopping a serum that stings.5