For OLP, some drugs (such as steroids, calcineurin inhibitors, retinoids, and anti-tumour necrosis factor (TNF) α therapies) must be used with serious precautions for topical, oral, or intravenous application, as they have deteriorating effects on certain comorbid diseases such as hypertension and diabetes, or, in some cases, they are fully contraindicated (breast feeding). This evidence concerns the gene TNF and oral lichen planus.