Propylene glycol is a ubiquitous, synthetic chemical that’s sometimes listed as E1520 and used in food, tobacco, pharmaceutical, and personal care products. Global propylene glycol production has been increasing in response to rising demand. Fifty percent of what’s produced is used in the manufacture of personal care and industrial products; the rest goes into the synthesis of other chemicals.
In the personal care product and pharmaceutical industry, propylene glycol is used as a vaporizer to deliver the relevant product. It also functions as a preservative, an antiseptic, a solvent, an emulsifier, and a moisture-regulating agent (humectant). It’s used in several topical steroid and pharmacologic formulations, and as plasticizer in many household items.
Propylene glycol exposure occurs mainly through skin absorption and ingestion. Skin exposure commonly occurs through contact with cosmetics and topical steroids. Some experts resent discrediting propylene glycol because, according to them, reactions in healthy skin are rare. However, several studies have documented its high sensitization potential, including allergic contact dermatitis, irritant contact dermatitis, contact urticaria (hives), and sensory or subjective irritation.
Both skin and oral exposure can produce itchy eczematous reaction. In a case reported in Dermatitis and documented in the National Center for Biotechnology Information (NCBI) Resources, a patient who experienced eczematous plaques on her face, neck, and right hand stopped using topical products containing propylene glycol and the dermatitis cleared up. However, they flared up once she started consuming foods that contained the chemical.
Although acute toxicity of propylene glycol is generally considered low, there’ve been reports of renal, cardiac, liver, as well as central nervous system, immune system and reproductive system toxicity. It can cause depression and ataxia, a lack of muscle coordination that impedes voluntary movements like walking, swallowing, and eye movements. Irritation of the eyes and subsequent conjunctivitis have been reported at high propylene glycol concentrations. People susceptible to eczema and fungal infections, but living in countries with limited sunshine, are likely to experience allergic contact dermatitis to propylene glycol. So far, there’s little evidence to suggest propylene glycol causes cancer.
Propylene glycol requires a lot of oxygen to degrade in the environment. This is problematic in aquatic ecosystems because the degradation process tends to deprive the organisms of much-needed oxygen.