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Sensitisation data (human)

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sensitisation data (humans)
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
no data
4 (not assignable)
Rationale for reliability incl. deficiencies:
other: Secondary literature

Data source

Reference Type:
secondary source
Bibliographic source:
The MAK collection for occupational health and safety; Occupational Toxicants, Vol. 14 (2000) []

Materials and methods

Type of sensitisation studied:
Study type:
not specified
Test guideline
no guideline followed
Principles of method if other than guideline:
Reports of contact allergies or photocontact allergies to thiourea or of photosensitivity to thiourea are rare. Usually diazo copy paper is the allergen source
GLP compliance:
not specified

Test material

Constituent 1
Chemical structure
Reference substance name:
EC Number:
EC Name:
Cas Number:
Molecular formula:
Details on test material:
- Name of test material (as cited in study report): Thiourea
- Substance type: organic
- Physical state: solid


Type of population:
Ethical approval:
not specified
Different case reports are summarized in the MAK collection for occupational health and safety for thiourea.
Clinical history:
Different case reports are summarized in the MAK collection for occupational health and safety for thiourea.
no data
Route of administration:
Details on study design:
Different case reports are summarized in the MAK collection for occupational health and safety for thiourea.

Results and discussion

Any other information on results incl. tables

- van der Leun et al. 1977: Photocontact dermatitis was developed on skin areas exposed to light by a 51-year old man three weeks after he started working at a copying machine. The photopatch test produced reactions to thiourea. The photosensitivity persisted although further contact with the copy paper was avoided.

- van der Leun et al. 1977: A 40-year-old black-skinned architect suffered from dermatitis on the hands and face. A marked increase in photosensitivity in the UVB range was diagnosed (no further details). A patch test revealed severe contact allergy to thiourea.

- Nurse 1980: A 41-year-old man developed dermatitis on the backs of his hands about one year after getting in contact with copy paper. The condition spread to the palms of the hands and finally also to the feet. Sunlight aggravated the condition of the hands. The patch test revealed reactions to exposed and unexposed copy paper, to a diazo compound (“Diazo 580”) contained in the paper and to a 1 % aqueous thiourea solution.

- Kellett et al. 1984: Dermatitis developed on the face, neck, arms and hands of a 24-year-old man who had contact with diazo copy papers at work. The patch test revealed reactions to thiourea (1 % in petrolatum and 0.01 % in water) and to exposed and unexposed diazo copy paper from the workplace. Increased sensitivity to UV light was not detected.

- Dooms-Goossens et al. 1987: A 40-year-old technical draughtsman who worked with blueprints by scratching printed lines off the paper, developed in the course of eight years a work-related skin disease. Dermatitis developed first in the middle of his face and in the perioral region and later spread to his forehead, neck and hands. Increased photosensitivity developed, first after exposure to sunlight, later also on exposure to neon light. Tests revealed increased sensitivity to UVA light and to visible light (400 nm). This sensitivity regressed if the patient was not at his workplace for weeks or months. Neither psoralen UVA treatment nor the intake of beta-carotene prevented a relapse after the man returned to his job. The patch test produced reactions to thiourea (0.5 %, 1 %, 2 % and 5 % in petrolatum and 5 % in water), but not to exposed or unexposed blueprints or paper scrapings from the workplace of the patient. In the photopatch test more pronounced allergic reactions to thiourea and to the paper scrapings were detected. According to information from the manufacturer, the thiourea concentration in the paper was about 0.04 mg/cm2, about a tenth of the concentration of the 2 % thiourea preparation in petrolatum used in the patch test. This could explain why the paper scrapings produced a reaction only in the photopatch test and not in the test without light, as radiation increased this patient's sensitivity to thiourea. The facial dermatitis of the patient was explained by paper scrapings flying about during the correction work, in other words by airborne contact with the allergen

- Dooms-Goossens et al. 1988: A 24-year-old woman cleaning silverware developed dermatitis on the tips of her fingers which, in the course of several months, spread to her arms and face. The primary location of the dermatitis was exactly the area of contact with the silver polish. Sun exposure to the skin worsened the condition. The patch test revealed contact allergy to thiourea (tests with 0.5 % in petrolatum and 5 % in water) which was contained in the silver polish used at the workplace. The patch test with thiourea (0.5 % in petrolatum) and exposure to light produced a stronger reaction than without exposure to light

- Niinimäki 1989: A 36-year-old plumber suffered from dermatitis on the ulnar side of the left hand which had direct contact with copy paper during drawing and correcting. The dermatitis spread to the arms and upper body. The photopatch test (UVA light, 5 J/cm2) produced a reaction to 0.1 % thiourea (vehicle not specified), while the patch test without exposure to light yielded negative results. The copy paper used by the man at work contained less than 1 % thiourea. The skin reactions ceased after the man changed his workplace

- Niinimäki 1989: A 40-year-old building contractor developed dermatitis mainly on the backs of the hands; in the course of several months it spread to his flanks and legs and became more severe on exposure to sunlight. In the photopatch test, photocontact allergy to thiourea was detected; the patch test without exposure to light yielded negative results. At work the patient had frequent contact with copy paper which, according to information from the manufacturer, was treated with a solution containing 4–5 % thiourea

- Pasche-Koo and Grosshans 1991: A 39-year-old man who had daily contact with diazo copy paper at work developed dermatitis on his hands, forearms and face. In the patch test, contact allergy to thiourea was detected but no other allergies. UV-sensitivity was normal. After the man changed to another workplace without contact with diazo copy paper, he suffered no further skin reactions

- Torres et al. 1992: A 44-year-old designer from an architect's office in which diazo copy paper impregnated with a solution containing 5 % thiourea was used developed contact allergy to thiourea. At first this was clinically manifested as dermatitis on the hands, later also as facial dermatitis, particularly in the periorbital region, as a result of transferring the allergen with the hands. The patch test with 0.1 % thiourea in petrolatum revealed a marked allergic reaction, the photopatch test with the same preparation an even more severe reaction. In the patch test the patient also produced allergic reactions to dimethylthiourea, exposed and unexposed diazo copy paper from the workplace and to hydroxylammonium chloride and sulfate. All three chemicals were contained in the paper.

- Geier and Fuchs 1993: A 29-year-old construction engineer worked for two years with diazo copy paper (blue prints) and then developed work-related dermatitis with small blisters on his hands and sometimes eczematous changes in the periorbital region. In the patch test, contact allergy to a diazonium compound from the blue prints and to thiourea, with which the paper was impregnated, was detected. A thiourea concentration of 0.1 % in petrolatum was used for testing.

- Bartels and Schauder 1994: In a 45-year-old telecommunications engineer who was employed mainly in system planning and had contact with diazo copy paper, dermatitis on the back of the hands that had existed for five years spread to areas exposed to light (face, neck). Exposure to sunlight made the condition of the skin worse. At first the results of the patch test were seen as an allergic reaction to the diazo copy paper used at work; three months later, however, the allergic reaction could not be reproduced in the control photopatch test without exposure to light. However, in the test areas exposed to light (UVA light, 3.3 J/cm2) reactions occurred against diazo copy paper containing thiourea and against thiourea (0.1 % in petrolatum). The patient was found to have increased sensitivity to UVA and UVB, which had not returned to normal even 294 days after ending contact with the diazo copy paper containing thiourea. The unusual thing about this case is that the sensitivity to UV light increased for more than 30 days after the end of exposure to thiourea. The authors do not comment on other photosensitizers with which the patient may have had contact.

- van Gerwen et al. 1996: A 37-year-old man who copied building plans using the diazo procedure at work and suffered from work-related dermatitis with small blisters on the hands produced a reaction to thiourea in the photopatch test. Data for the test concentration, for UV sensitivity and for the further course of the disease are lacking.

- Roberts and Hanifin 1980: Of seven patients with known contact allergy to ethyl butyl thiourea, one also reacted in the patch test to 0.063 M thiourea in petrolatum.

- Hölzle 1991: Thiourea (0.1 % in petrolatum) was tested between 1985 and 1990 in 45 dermatological centres in Austria, Germany and Switzerland using the photopatch test. How many of the 1129 patients were tested with thiourea, was not specified. Phototoxic reactions were observed in 0.18 % of those tested, non-classifiable photoreactions in 0.55 % and a photoallergic reaction in none of the patients. Contact allergic reactions occurred in 0.92 % of those tested. No information is given on the clinical relevance of these reactions.

Applicant's summary and conclusion

Relative to the number of persons exposed to thiourea, for example through contact with diazo copy paper, the number of reported contact and photocontact allergies to thiourea is small. In addition it is often not clear whether or not the patient was exposed to thiourea as such, thiourea derivatives or additional compounds in a mixtures. The MAK Komission concluded in 2000 that "In view of the usually grave consequences for those affected, contact or photocontact allergy to thiourea, in particular with the development of a persistent reaction to light, thiourea has nevertheless been designated with “Sh” and “SP” (for substances where there is a danger of sensitization of the skin and of photocontact sensitization)." However, this does not justify a classification of thiourea as skin sensitizer under CLP.