Recurring Itchiness

Hi! I’ve recently tried The Ordinary’s Azelaic Acid Suspension 10% about 3 days ago, twice a day — morning and night. I always start by double cleansing followed by a hydrating toner before putting it on my face and then I finish it off with a moisturizer. It’s been great so far and I love the texture. But what’s baffling me is sometimes it’s itchy on some parts of my face, and sometimes it doesn’t itch at all. Is this normal when just starting with it? Or should I stop it? Let me know below. Thanks!