Mercury is usually added to skin-lightening products due to its whitening effect.
The Food and Drug Administration (FDA) limits the amount of mercury in cosmetics to
trace amounts under 1 ppm. Nevertheless, many cosmetics contain mercury above 1000
ppm to increase the whitening effect. In a group of special patients in the study,
pain, renal damage, and neuropsychiatric symptoms were the cardinal symptoms observed.
The present study included 16 female patients diagnosed with chronic mercury intoxication
at the First Affiliated Hospital of Zhengzhou University from 2009 to 2017. The age
of these patients ranged from 19 to 50 years. All the 16 patients had a flexuose treatment
experience, slow onset, and a hidden history that contributed the delayed diagnosis.
There was no history of exposure to mercury in their work, but all of them had a history
of using skin-lightening products, which had immediate and dramatic whitening effects.
The chief complaint was miserable pain, and limb, head, abdomen, or lumbosacral pain
was poorly responsible for nonsteroidal anti-inflammatory drugs, anti-epileptic drugs,
and serotonin-norepinephrine reuptake inhibitors. According to the World Health Organization
visual analog scale ranking, 0 referred to no pain and 10 referred to baryodynia.
The pain of these 16 patients was rated between 4 and 7. Renal damage was another
characteristic, in which six of all the patients presented with proteinuria. In addition,
all patients had varying degrees of irritability, insomnia, dreams, depression, anxiety,
and memory loss. Furthermore, five patients presented with eyelid, tongue, or limb
tremors, while three patients presented with gingivitis.
The 24-h urine mercury content of these patients was within 0.037–0.170 mg/L (normal
value, <0.010 mg/L). In one skin-lightening product sample, the mercury concentration
was found to be 19,742 ± 379 ppm, which is 19,000 times higher than the FDA limit.
The electromyography examination was normal in 11 patients, while it was abnormal
in five patients; and slow sensory nerve conduction velocity and reduced amplitude
were mainly observed. Moreover, the brain magnetic resonance imaging and lumbar puncture
of seven patients with headache were normal. Hamilton Depression Scale-17 (HAMD-17,
normal value <7 points) scores were within 9–20 points [Supplementary Table 1]. All
patients received intravenous sodium dimercaptopropane sulfonate at 0.125 g/d and
other symptomatic treatments.
Supplementary Table 1
Signs, symptoms, and other findings of these patients
Case
Age (years)
Latency from using the product to symptom onset (weeks)
Avenue of purchase
Main symptoms
Accompanied symptoms and signs
VAS ranking
Urine mercury
EMG
HAMD score
1
36
4
Online
Headache, back pain
Hypomnesia, insomnia, irritability, often cries
6
0.160 mg/L
Conduction velocity of the bilateral endings of the median sensory nerve was slower,
and the amplitude decreased
25
2
33
6
Online
Pain in the four limbs, abdominal pain
Eyelid tremor, finger tremor, irritability, distraction, renal damage
6
0.140 mg/L
Normal
18
3
30
9
Online
Pain in the four limbs
Both hand tremor, distracted, insomnia, renal damage
7
0.170 mg/L
The amplitude of the bilateral common peroneal nerve decreased
16
4
37
13
Beauty shop
Headache and pain in the four limbs
Insomnia, gingivitis
5
0.110 mg/L
Normal
13
5
40
5
Beauty shop
Foot pain
Difficulty in falling asleep, distracted
5
0.090 mg/L
Normal
10
6
19
7
Online
Lumbosacral pain, abdominal pain
Eyelid tremor, lingual tremor, hand tremor, insomnia, gingivitis, renal damage
6
0.150 mg/L
Conduction velocity of the bilateral tibial and peroneal sensory nerve was slower,
and the amplitude decreased
26
7
39
10
Online
Pain in the four limbs
Difficulty in falling asleep
4
0.037 mg/L
Normal
17
8
35
6
Store
Headache and pain in the four limbs
Renal damage, insomnia
6
0.120 mg/L
Normal
10
9
29
8
Store
Pain in the four limbs
Insomnia, distracted
4
0.080 mg/L
Normal
12
10
36
5
Store
Pain in both lower extremities, lumbosacral pain
Insomnia, distracted, hypomnesia, irritability
6
0.130 mg/L
Conduction velocity of the bilateral tibial and sensory nerve was slower, and the
amplitude decreased
22
11
32
7
Online
Pain in both lower extremities and lumbosacral pain
Renal damage
4
0.106 mg/L
Normal
19
12
27
5
WeChat shop
Pain in both lower extremities and abdominal pain
Lingual tremor, hand tremor, insomnia, gingivitis, irritability
6
0.120 mg/L
Normal
21
13
42
8
Beauty Shop
Headache and pain in the four limbs
Limb tremor, hypomnesia, insomnia, irritability, renal damage
6
0.110 mg/L
Normal
24
14
41
12
Online
Pain in the four limbs
Difficulty in falling asleep, irritability
4
0.076 mg/L
Normal
16
15
50
11
Store
Headache, pain in the four limbs
Hypomnesia, insomnia, irritability
5
0.130 mg/L
Normal
15
16
33
12
Online
Pain in both lower extremities and abdominal pain
Irritability, insomnia, renal damage, hypomnesia
6
0.110 mg/L
Conduction velocity of the bilateral tibial and sensory nerve was slower, and the
amplitude decreased
24
VAS: Visual analog scale; EMG: Electromyography; HAMD: Hamilton Depression Scale.
Mercury ions replace tyrosinase enzyme anions, which inhibit the formation of melanin
and produce the whitening and anti-freckle effects.[1] Some products are added with
the mercury content, which exceeds bid badly in thousands or even millions of times,
in order to make the lightening effect remarkable. The long-term usage of these unqualified
products would induce chronic mercury poisoning.
The common symptoms of chronic mercury poisoning are irritability, tremor, and gingivitis,
while the onset of pain is rare. Furthermore, it has been reported that it causes
memory loss, dizziness, insomnia, dreams, edema, proteinuria, abdominal pain, nausea,
hyperthyroidism, and abortion. Studies on mercury poisoning, which leads to peripheral
nerve damage, are rare. Patients in the present study prominently complained of pain,
but rarely referred to limb weakness. Distal extremity hypoalgesia was not observed,
and all patients had no severe central nervous system symptoms, such as lags in response,
seizures, confusion, difficulty in swallowing, glossolalia, deafness, narrow field
of vision, strabismus, or photophobia, which were similar with Minamata disease.[2]
Mercury damages the nerves in several ways: it interferes with membrane and receptor
functions, and neurotransmitter transport and metabolism; it interrupts cytoskeletal
proteins, and interferes with axoplasmic flow and signal transduction; it interferes
with cell respiration, energy metabolism and others.[3] Among the 16 patients, six
patients presented with proteinuria, but without edema. After 3–5 courses of chelation
treatment, urine mercury returned to normal levels. Then, after approximately 4–8
weeks, pain was alleviated, urine protein was negative, and HAMD scale scores returned
to normal.
Unqualified products that contain toxic substances such as mercury are not rare. These
substances usually damage the nervous and renal systems. Hence, history taking is
all important, and mercury chelation treatment should be given after diagnosis as
soon as possible. Furthermore, the public should be warned about this danger.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form, the patients/patients’ guardians have given their consent for their images
and other clinical information to be reported in the present study. The patients/patients’
guardians understand that their names and initials will not be published, and due
efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Supplementary information is linked to the online version of the paper on the Chinese
Medical Journal website.
Financial support and sponsorship
This study was supported by grants from the National Natural Science Foundation of
China (No. 81501111), and the Henan Provincial Major Scientific College Project (No.
18A320065).
Conflicts of interest
There are no conflicts of interest.