Parabens – What Are They?
Parabens (parahydroxybenzoates, PHD) are a series of esters of 4-hydroxybenzoic acid that differ in their functional group. Depending on this group, they are designated by the codes E214, E215, E216, E217, E218, and E219.
They act as preservatives, which is why they are used in cosmetics, medicines, and food products:
- in toothpaste, foundation, creams, lotions, lip balms, face masks, shampoos, soaps, and toners,
- in eye ointments and eye drops—including antiallergic ones—as well as in diabetes medications and anesthetics (e.g., lidocaine), in topical steroids, cough suppressants, antidepressants, antihistamines, and over-the-counter pain relievers (e.g., headache tablets),
- in salads, ketchup, mayonnaise, canned fish, boxed juices, lemonade, jams, and cookies (in this form, they rarely cause allergic reactions, and when they do, it is more common among food service workers than among consumers).
PHDs are weak contact allergens, but the relatively common sensitivity to them is due to the extent of exposure and ranges from 0 to 4.2% of those tested or—according to more recent sources—0.7–2.3% of patients undergoing patch testing [1].
Recognizing Symptoms and Their Causes
The typical presentation of an allergy includes:
- itchy skin papules of varying severity,
- eczema-like lesions on the hands or lower legs,
- resolution of the lesions during vacation.
Note: Rashes may appear on areas of the skin distant from the site of direct contact! The more frequently an eczema flare-up occurs, the sooner a patch test should be performed and elimination measures taken. Patient interviews, in which the patient describes the circumstances surrounding the onset of symptoms, along with a physical examination, usually identify the list of these allergens. The PHD blend used in the Polish Basic Series (PSP) and the KRAK series contains equal parts (4% each) of E214–E219 and butylparaben [1]. An allergy to PHD is characterized by some interesting paradoxes, two of which I have observed.
The first paraben paradox—skin condition
The first phenomenon, known as the “paraben paradox,” is that patients with an allergy to PHD in topical medications tolerate cosmetics containing the same preservative well. This is due to differences in allergen penetration through healthy skin and skin affected by inflammation, as well as to PHD concentrations higher than 0.19%. These changes are particularly common in older adults and those with chronic illnesses. Parabens are very easily absorbed through leg ulcers [2]. People with atopic dermatitis also constitute a group at increased risk of PHD sensitization.
The Second Paraben Paradox—Unfounded Concerns?
Toward the end of the 20th century, numerous concerns arose regarding the harmful effects of PHD. Parabens belong to a group of compounds called xenoestrogens. These substances have a structure similar to that of natural estrogens and can alter the functioning of the endocrine (hormonal) system; hence, they are referred to as endocrine-active compounds or endocrine disruptors. Methylisothiazolinones (MI) were identified as substitutes and soon became widely used preservatives in a wide range of cosmetic and household products, such as:
- moist wipes,
- toilet paper,
- shower gels and shaving gels,
- shampoos,
- liquid soaps,
- exfoliants,
- makeup removers and intimate hygiene products,
- laundry detergents,
- cleaning liquids.
Shortly thereafter, the Scientific Committee on Consumer Safety (SCCS)—based on previous studies—indicated that MI is a stronger contact allergen than PHD, and that individuals with a confirmed allergy to MI should avoid products containing this preservative. In Poland, Kręcisz et al. [3] found, among 405 patients, that MI was the most common sensitizing agent (4.7%), while parabens were the least common (0.2%).
Thus, the attempt to replace PHDs—which are supposedly more allergenic and harmful—with MI turned out to be, as the saying goes, jumping out of the frying pan into the fire. Currently, PHDs are among the most thoroughly studied preservatives, but there is no absolute certainty that they are not harmful. However, it has been demonstrated that they are neither carcinogenic nor toxic, do not accumulate in tissues, and do not affect human hormonal balance [4].
Cross-Reactions
A cross-reaction is an allergic reaction to substances with a chemical structure similar to that of the original sensitizing substance. In individuals sensitized to PHD, cross-allergy may occur to compounds containing a benzene ring, the best-known example of which is paraphenylenediamine (PPD).
Therefore, in cases of confirmed allergy to parabens, patch tests should be performed using the “PPD Cross-Reactions” series, which includes dyes, sulfonamides, photographic reagents, rubber antioxidants, etc. American authors reported that the incidence of PPD-PHD cross-reactions and paraben-benzocaine cross-reactions is only 2% and is significantly lower than originally thought. In Poland, these figures are higher (2.6% and 6.2%, respectively) [3].
Recommendations from an allergist
If a contact allergy to PHD is detected and confirmed, patients should simply use cosmetic products or medications that do not contain preservatives to which they are allergic. It’s best to look for labels that say “paraben-free”, which clearly indicate that the product does not contain these substances, or to check the list provided at the beginning of this article to see if any ingredients in the E214–E219 group are present in your personal collection of cosmetics.
When it comes to food—don’t panic, but try avoiding all foods containing parabens for 5 days, and then reintroduce them into your diet one at a time every 4 days. It often turns out that minimal amounts of food preservatives do not trigger an allergic reaction and can be consumed without any problems, though it’s best not to do so too often.
For people who have never had a PSP test or a similar test, it is difficult to take reasonable preventive measures. Therefore, if you have itchy eczema, you should find a good allergist and get to the bottom of the issue.
