Dry mouth from Diphenhydramine

Dry mouth, medically known as xerostomia and colloquially referred to as cottonmouth, is defined as a noticeable and often uncomfortable reduction in saliva production that causes the mouth, tongue, and throat to feel parched, sticky, and difficult to swallow through. Saliva production is regulated by the autonomic nervous system, and many psychoactive substances interfere with the parasympathetic signals that stimulate the salivary glands, resulting in a mouth that feels as though it has been stuffed with cotton or dusted with chalk.

The subjective experience of dry mouth ranges from a mild awareness of reduced moisture in the oral cavity to an acutely uncomfortable state in which the tongue adheres to the roof of the mouth, the lips crack and peel, speaking becomes effortful, and swallowing food without liquid assistance becomes nearly impossible. The throat may feel scratchy and irritated, and there is often an accompanying sense of thirst that is not fully satisfied by drinking water, as the dryness stems from suppressed salivary gland activity rather than systemic dehydration alone.

Dry mouth is one of the most ubiquitous side effects across the spectrum of psychoactive substances. It is most commonly induced under the influence of moderate dosages of cannabinoids (where it is perhaps most famously associated), stimulants, psychedelics, opioids, anticholinergics, antipsychotics, deliriants, and SSRIs. Cannabis produces dry mouth primarily through cannabinoid receptor activation in the submandibular glands, while stimulants and anticholinergics reduce saliva through sympathetic nervous system activation and parasympathetic blockade respectively. The precise mechanism varies by substance class, but the subjective result is consistently similar.

Dry mouth is often accompanied by other coinciding effects such as dehydration, increased water consumption, and frequent urination (the latter resulting from drinking large amounts of water to combat the dryness). It can also co-occur with difficulty swallowing, altered taste perception, and an unpleasant metallic or chemical taste in the mouth. During prolonged experiences, the persistent dryness can make eating solid food uncomfortable and may contribute to a sore throat the following day.

As a basic harm reduction practice, one should stay consistently well hydrated by sipping water or other non-caffeinated beverages regularly throughout the experience. Sucking on sugar-free candy or ice chips can help stimulate residual salivary gland activity. Breathing through the nose rather than the mouth reduces evaporation of whatever moisture is present. Avoiding caffeine and alcohol, both of which have additional drying effects, can also help minimize the severity of dry mouth during substance use.

While acute dry mouth during substance use is generally benign and self-limiting, chronic xerostomia from prolonged or frequent substance use poses genuine health risks. Saliva plays a critical role in neutralizing acids, washing away food particles, and providing antimicrobial protection in the oral cavity. Persistent reduction in saliva flow is associated with accelerated tooth decay, gum disease, oral infections (particularly candidiasis), difficulty wearing dentures, and impaired wound healing in the mouth. Individuals who regularly experience substance-induced dry mouth should maintain excellent oral hygiene and consider using saliva substitutes or stimulants.