Smoking, in addition to its other harmful effects on our health, also weakens our defence against HPV. To be precise, it restricts the action of certain cells of our immune system (such as the Langerhans cells) which are responsible for suppressing the virus locally, in the tissues of the lower genital tract. It has also been proven that carcinogenic substances in tobacco (such as benzopyrene, cotinine, phenols, etc) can be detected in the cervical mucus of women who smoke (in a much higher concentration than in the blood) and they may act as contributing factors in carcinogenesis.
