Persistent whiteheads occur when pores are continually clogged by excess oil and dead skin. To prevent them from recurring, you need treatments that keep pores clear rather than just removing them. I recommend using topical salicylic acid, which penetrates deep into the pores to dissolve oil blockages. Additionally, applying a topical retinoid, such as adapalene, at night is highly effective because it accelerates skin cell turnover and prevents new clogs from forming. Be sure to use a gentle, non-comedogenic moisturiser to prevent dryness. It may take 4 to 6 weeks to see improvement, so consistency is key. If irritation occurs, consult a dermatologist.