What is benzalkonium chloride?
Benzalkonium chloride is an organic salt used in cleaning agents, classified as a quaternary ammonium cationic detergent. It can be used as an antiseptic and preservative in personal care, healthcare, household, pharmaceutical, and industrial products [1,2].
What is benzalkonium chloride contact dermatitis?
When benzalkonium chloride comes into contact with the skin, it can cause irritant contact dermatitis or allergic contact dermatitis in some individuals.
Benzalkonium chloride is a well-known irritant . Irritant contact dermatitis due to benzalkonium chloride is more common than allergic contact dermatitis from its use.
Who gets benzalkonium chloride contact dermatitis?
Irritant contact dermatitis due to benzalkonium chloride can affect anyone. Allergic contact dermatitis can affect any individual who becomes sensitised or allergic to benzalkonium chloride.
Both irritant and allergic contact dermatitis due to benzalkonium chloride are more likely to occur in people with a compromised skin barrier, such as in people with atopic dermatitis (eczema).
Healthcare workers are also at greater risk of developing contact dermatitis to benzalkonium chloride, given the use of benzalkonium chloride use in sterilisation solutions and antiseptics and disinfectants in healthcare settings [2,3].
Where is benzalkonium chloride found?
Benzalkonium chloride can be found in:
- Household cleaning products, such as laundry rinses/detergents 
- Personal care products 
- Moisturisers, make-up removers, and cleansers
- Shampoos and hair products
- Wet wipes
- Antiseptics 
- Eye drops and ophthalmic solutions, including :
- Glaucoma treatments
- Antibacterial eye drops
- Corticosteroid eye drops
- Antihistamine eye drops
- Lubricating eye drops/artificial tears
- Contact lens solutions
- Nasal sprays and asthma inhalers (tiotropium)
- Dental products
- Plaster of Paris [8,9]
- Sterilisation solutions for medical instruments 
- Industrial products used in:
- Fabrication of textiles and dyes .
How does benzalkonium chloride contact dermatitis present?
Both allergic and irritant contact dermatitis start at the site of contact with benzalkonium chloride. In prolonged or severe cases, dermatitis may spread to other sites [10,11]. The affected skin may be red, itchy, dry, or scaly, and may also blister or peel.
Symptoms may start to occur hours or days after contact with benzalkonium chloride. Some people may develop periorbital or eye dermatitis or conjunctivitis (red and itchy eyes) after the use of ophthalmic solutions containing benzalkonium chloride .
A small subset of people exposed to benzalkonium chloride may develop a rash called granular parakeratosis . Granular parakeratosis is a red or brown patchy and scaly rash that most commonly affects skin folds such as the armpits and groin. As the skin heals, it might peel .
It is thought that, in addition to being provoked by occlusion, friction, and sweating, granular parakeratosis can also be provoked by contact with benzalkonium chloride. People with atopic dermatitis are predisposed to this condition [4,12].
Granular parakeratosis due to contact with benzalkonium chloride
How is benzalkonium chloride contact dermatitis diagnosed?
Patch testing is used to diagnose allergic contact dermatitis (type IV/delayed hypersensitivity) to benzalkonium chloride. Benzalkonium chloride is included in the Australian baseline series for patch testing (tested as benzalkonium chloride 0.1% aqueous) .
Doubtful or weakly positive patch test reactions to benzalkonium chloride should be interpreted cautiously. These weak positive reactions may represent irritant reactions, rather than allergic reactions [5,14].
The open application test may also be useful to confirm reactions .
Doubtful patch test reaction to benzalkonium chloride
What is the treatment for benzalkonium chloride contact dermatitis?
Once the diagnosis of contact dermatitis is confirmed, it is important to avoid contact with any product containing benzalkonium chloride. The affected individual should be aware of the types of products that can contain benzalkonium chloride and should carefully read product ingredient labels.
The avoidance of benzalkonium chloride along with treatment for the acute dermatitis usually results in resolution of the rash over weeks.
In cases of contact allergy, it is likely that the individual will remain allergic to benzalkonium chloride indefinitely, or at least for many years.
Benzalkonium chloride can cross-react with other quaternary ammonium compounds (preservatives), such as behentrimonium methosulfate, cetrimonium (cetrimide) chloride, and benzethonium chloride . If someone is found to have allergic contact dermatitis to benzalkonium chloride, they should avoid the following ingredients as well:
- Alkyl dimethyl benzyl ammonium chloride
- Alkyl dimethyl ethyl benzyl ammonium chloride
- Behentrimonium methosulfate
- Benzethonium chloride
- Cetrimonium (cetrimide) chloride
- Cetylpyridinium chloride
- Distearoylethyl dimonium chloride
- Guar hydroxypropyltrimonium chloride .
Active dermatitis can be treated, as with any acute eczema/dermatitis, with:
- Topical steroids
- Tacrolimus ointment or pimecrolimus cream
- Oral medications if required.