CASE REPORT
An otherwise healthy 23‐year‐old woman presented with facial symmetrical erythema
and slight itching lasting 4 days. Symptoms developed after wearing a KN95 (FFP2 equivalent)
mask for 2 days to prevent contracting SARS‐CoV‐2. One day before, the patient had
consulted the emergency department and a presumptive diagnosis of acute cutaneous
lupus erythematosus by the general emergency doctors was made because of her gender
and facial symmetrical erythema. However, the physical examination and medical history
of the patient and her family were unremarkable. Blood and urine routine tests and
the erythrocyte sedimentation rate were negative and normal, respectively. The specific
autoantibodies and complement were also negative.
In our dermatology clinic, given the use of the mask and the shape of the lesion resembling
that of the sponge strip on the contact surface inside the mask (Figure 1), the patient
was provisionally diagnosed with mask‐induced allergic contact dermatitis (ACD). After
3 days of anti‐allergic treatment (oral desloratadine and topical desonide cream),
the lesions almost completely disappeared. The patient switched to other masks without
sponge strips which were tolerated. No recurrence was found after 3‐month follow‐up.
FIGURE 1
Symmetrical erythema centered on the nose bridge without blisters and scales. The
highlighted area shows the same pattern of rash as the sponge strip on the contact
surface of the mask
Patch tests were applied on the upper back and occluded for 2 days with the TRUE Test
(Mekos Laboratories, Hillerød, Denmark), and readings were made on day (D)2, D4, and
D7 with negative results.
1
Additional patch tests using IQ chambers (Chemotechnique Diagnostics, Vellinge, Sweden)
were performed with pieces of sponge taken from this mask. Tests were read on D2 and
D4 according to ESCD guidelines and showed a positive reaction to the sponge (++)
at D4, while no reaction was seen in three self‐controls (D4) (Figure 2A). Ten control
volunteers were patch‐tested the same way with all negative results. The patient was
then tested with the isocyanate series (Chemotechnique Diagnostics) and showed a positive
reaction to toluene‐2,4‐diisocyanate (TDI) 2.0% pet., 4,4'‐diaminodiphenylmethane
(MDA) 0.5% pet., and hexamethylene diisocyanate (HDI) 0.1% pet. on day D2 (++) and
D4 (++) (Figure 2B).
FIGURE 2
(A) Patch tests showed a positive reaction (++) to the sponge strip (b) and three
negative results, including metal strip (a), blank control (c), and polypropylene
spun bond non‐woven fabric (d) on day 4. (B) On D4, positive patch test reactions
to TDI 2.0% pet. (1), MDA 0.5% pet. (3), and HDI 0.1% pet. (6)
DISCUSSION
Polyurethanes, which are being used increasingly in the production of various products,
including the sponge strip inside the mask, are produced by the reaction of diisocyanates
and may cause ACD or precipitate asthma attacks.2, 3 Polyurethane as the fully cured
polymer is thought not to be a sensitizer. However, residual cross‐linkers have been
reported to cause allergic reactions, such as TDI, HDI, MDA, or MDI, which are particularly
responsible for respiratory symptoms, and less frequently for ACD.4, 5 To our knowledge,
this is the first case report of ACD to a polyurethane sponge inside a mask.
Facial ACD can mimic other diseases, such as acute cutaneous lupus erythematosus,
seborrheic dermatitis, and sarcoidosis, especially if occurring on specific body areas
or evaluated by a nondermatologist. At present, the use of masks is very common due
to the COVID‐19 pandemic. The incidence of allergies caused by mask contact may increase.
Meanwhile, during the epidemic, all medical staff need to wear medical masks much
longer than the general population, which may easily lead to local impression, redness,
erosion, and even induce eczema or worsen rosacea. In this special period, all doctors,
especially emergency doctors or general practitioners who are responsible for the
main admissions during the pandemic, must be vigilant to help avoid delaying diagnosis,
unnecessary tests, and causing panic among patients.
CONFLICT OF INTEREST
The authors have no conflicts of interest to disclose.
AUTHOR CONTRIBUTIONS
Zhen Xie: Conceptualization; investigation; resources; writing‐original draft. Xin
Yang: Conceptualization; investigation; project administration; resources; writing‐review
and editing. Hao Zhang: Conceptualization; investigation; project administration;
resources; supervision; writing‐review and editing.