Contact allergy to parabens

What are parabens?

Parabens are synthetic preservatives, widely used in cosmetics, food, and topical pharmaceuticals for over 70 years to prevent the growth of microorganisms.

Parabens are a family of alkyl esters of para-hydroxybenzoic acid and include methyl-, ethyl-, propyl-, butyl- and benzylparaben. Benzylparaben is no longer commonly used.

As many products contain two or more paraben esters and there is a high incidence of cross-reactions between the esters, it is useful to test paraben sensitivity with paraben mix.

In 2019, parabens were named the ‘non-Allergen’ of the Year by the American Contact Dermatitis Society, due to the low frequency of reactions despite high prevalence of use.

Where are parabens found?

Parabens are commonly found in cosmetics, food, and topical pharmaceuticals.

Some studies and databases have shown parabens are present in up to 21% of household products, including 66–87% of cosmetics and 99% of leave-on cosmetic products.

Table 1. Uses of parabens

Parabens can also be found in shoe polish, glues, textiles, pet care products, metal-working oils/fluids, and agriculture-food production.

Different regions have varying regulations about which parabens can be used, and at what concentration. Usually individual parabens can be used at concentrations of 0.4% or less, and up to 0.8% as mixtures. Benzylparaben is not used in the European Union (EU), and propyl- and butylparaben can only be used at 0.14% together.

Who gets contact allergy to parabens?

The prevalence of contact allergy to parabens in the general population is unknown. An analysis of all screening studies over the last 50 years showed that 1.2% of patients who underwent patch testing had positive reactions to parabens. However, rates have decreased over time with the introduction of concentration limits, so this figure is likely a current overestimation.

Contact allergy most commonly occurs to topical medications and bandages used on damaged skin. This is usually over leg ulcers or eczematous areas.

Hand dermatitis has been described in cooks and food handlers working with food containing parabens.

What are the clinical features of contact allergy to parabens?

Allergy to parabens usually presents as an allergic contact dermatitis. This is a type 4 (delayed) immunological hypersensitivity reaction occurring 48–72 hours after exposure to the allergen. Localised erythema, pruritus, swelling, or blistering can develop in areas of skin contact. Sometimes it may be seen as a flare or spread of an existing rash.

Rarely, there can be irritant contact dermatitis to parabens, which is a non-immunological reaction that develops when an agent damages the skin surface faster than it can be repaired.

There are also some descriptions of contact urticaria.

It is very rare to get systemic contact dermatitis or allergic reactions from oral ingestion of parabens.

How do clinical features vary in differing types of skin?

Erythema may be more difficult to appreciate in darker skin types, and postinflammatory hyperpigmentation is more common.

What are the complications of contact allergy to parabens?

Complications of contact allergy to parabens can include:

• Secondary skin infection eg, bacterial skin infections
• Post-inflammatory hypopigmentation or hyperpigmentation, with aesthetic concerns
• Lichenification if there is chronic inflammation.

How is contact allergy to parabens diagnosed?

Contact allergy to parabens is diagnosed by history, examination, and patch testing.

Patch testing preparations vary geographically. Usually a paraben mix of 4 or 5 individual parabens is used, at a concentration of 12–16% paraben mix in petrolatum. Benzylparaben is not part of the European series.

Paraben mix can give false positives, with negative results when tested individually. When reactions occur they are usually weak.

Patch testing with own products is often negative, because the concentrations are too low. It can also be complicated as many products contain multiple preservatives. Repeated open application testing may be considered.

What is the treatment for contact allergy to parabens?

For anyone diagnosed with paraben allergy, education about and avoidance of paraben-containing products is important. Parabens do not routinely need to be avoided in foods and oral medications, as allergy from ingestion is very rare. If the reaction has occurred on areas of damaged skin, people can often tolerate paraben-containing cosmetics on non-damaged skin.

If contact dermatitis occurs, treatment is as for any acute dermatitis/eczema:

• Topical corticosteroids (those not containing paraben preservatives)
• Emollients
• Treatment of secondary bacterial infection (eg, from Staphylococcus aureus).

For more information, see irritant contact dermatitis and allergic contact dermatitis.

Avoiding parabens

If you have a contact allergy to parabens, you will need to identify potential sources of parabens and try to avoid them. This can be difficult because of their widespread use.

Try to use topical products with clearly marked ingredients that do not contain parabens. Parabens are also known by several other names (see below). Databases can be used to research which items contain parabens (eg, Contact Allergen Management Program, SkinSAFE). If unsure about medication, ask your pharmacist for advice. If contact is unavoidable, consider using protective gloves.

Other related substances you may also react to include para-aminobenzoic acid (PABA) esters and paraphenylenediamine.

Alert your doctor, dentist, beautician and hairdresser to the fact that you have an allergy to parabens. If you are in contact with parabens at work, talk to your employer or occupational health about modifications. Your dermatologist may have further specific advice, particularly if you are highly sensitive.

Alternative names for parabens

Methylparaben:

• Methyl p-hydroxybenzoate
• 4-hydroxybenzoic acid methyl ester
• Methyl parahydroxybenzoate
• P-methoxycarbonylphenol.

Ethylparaben:

• Ethyl p-hydroxybenzoate
• 4-hydroxybenzoic acid ethyl ester
• Ethyl p-oxybenzoate
• P-carbethoxyphenol.

Propylparaben:

• Propyl p-hydroxybenzoate
• 4-hydroxybenzoic acid propyl ester.

Butylparaben:

• Butyl p-hydroxybenzoate
• 4-hydroxybenzoic acid butyl ester.

Benzylparaben:

• Benzyl p-hydroxybenzoate
• Phenylmethyl 4-hydroxybenzoate
• P-hydroxybenzoic acid benzyl ester.

What is the outcome for contact allergy to parabens?

Symptoms usually settle once the allergen (or irritant) is identified and avoided. Continuous exposure (such as at work) can cause chronic symptoms.

Further information

Table 2. Parabens, chemical formula and CAS number

Food additive E number: E210-219

Cross reactions:

• Para-aminobenzoic acid (PABA) esters
• Paraphenylenediamine.

Sensitiser: paraben esters

Patch test: paraben mix 12–16% in petrolatum (3–4% each of methyl-, ethyl-, propyl-, and butyl-parahydroxybenzoate); or available in pre-prepared T.R.U.E.® test.

Notes: There has been much debate about the wider safety of parabens (particularly regarding hormonal effects, fertility and concerns about links to breast cancer); they have been classified as generally regarded as safe by the US Food and Drug Administration.