A dermatologist explains that makeup primer creates a smoother base, blurs pores, controls oil, and helps makeup last longer by reducing direct skin contact. Skipping primer can lead to foundation settling into lines, patchy coverage, and a dull appearance, especially in humid weather. While not a direct cause of breakouts, makeup applied directly to bare skin may clog pores, particularly for oily or acne-prone individuals, potentially increasing the risk of pimples or irritation over time.