Indian Journal of Dermatology
: 2007  |  Volume : 52  |  Issue : 4  |  Page : 199--200

Dermatitis due to straw itch mite in Assam

Reema Nath1, Lahari Saikia1, M Choudhury1, J Mahanta2,  
1 Department of Microbiology, Assam Medical College, Dibrugarh - 786001, Assam, India
2 Regional Medical Research Centre, Dibrugarh - 786001, Assam, India

Correspondence Address:
J Mahanta
Regional Medical Research Centre, Post Box-105, Dibrugarh - 786 001, Assam


Mites belonging to Pyemotidae family are an important cause of human dermatoses. Though their bites are painless, yet, afterwards severe itching and possible secondary infection. Most of the time mites could not be demonstrated from the lesion. We are presenting a case where mites could be seen in scrapping from a typical lesion in man.

How to cite this article:
Nath R, Saikia L, Choudhury M, Mahanta J. Dermatitis due to straw itch mite in Assam.Indian J Dermatol 2007;52:199-200

How to cite this URL:
Nath R, Saikia L, Choudhury M, Mahanta J. Dermatitis due to straw itch mite in Assam. Indian J Dermatol [serial online] 2007 [cited 2020 Jun 2 ];52:199-200
Available from:

Full Text

A 40-year-old male, came to the Dermatology outpatient department of Assam Medical College and hospital with severe itching and red papular lesions of the face of about 20 days duration. The lesions first started in the left cheek and were gradually spreading to the lips, forehead and the other cheek. Some of the lesions had blisters with watery discharge and a few of them had small white pustule at the center [Figure 1]. The patient did not remember any insect bites. He was afebrile and without any rash or joint pain. He gave history of aggravation of itching on exposure to sunlight. He works as a manual worker in a local bakery. There was no family history of any allergy or recurrent skin infections. He did not have any history of close contact with pets or domestic animals. His body temperature was normal, blood pressure 120/70. Routine blood examination showed mild eosinophilia. No abnormality could be detected in the systemic examination. A provisional diagnosis of grocer's itch or baker's itch was made. However, to exclude fugal etiology skin scrapping was requested. Scrapping from the lesion did not reveal any fungal element in KOH mount. However, one adult living mite and several disintegrated legs and other parts were seen under microscope.

The insect was 200 , in length with eight jointed legs. It was initially identified as an itch mite. The specimen images were sent to an entomology expert of Center for Disease Control, Atlanta, who opined the mite to be a non-gravid female mite belonging to Pyemotidae family [Figure 2].

Acarine dermatosis is getting importance for accidental and temporary human infection of which Pyemotes mite is one of them. Pyemotes mites are ecto-parasite of many insect species. Normally they infest grass or grain and attack insect larvae. However, they can attack humans, if their normal food sources are reduced. [1] Bites are painless and red welts with a small white pustule in the center may appear after about two to 24 hours. Severe itching and possible secondary infection can occur due to repeated scratching and itching may last up to several weeks. Besides dermatitis, cases can develop fever, vomiting and joint pain. [1] Of course popular eruption to extensive skin eruption along with chill, fever, malaise, diarrhea, anorexia etc. have also been reported. The mites reside only briefly on humans and the parasite usually leaves the host with the beginning of itching. [2] They are not visible to the naked eye and thus the victim or the physician misses them during clinical examination. Therefore, diagnosis is often made from clinical features and circumstantial evidences like; patient's environment and the infested materials in the patient's environment. [2],[3],[4] Infested wheat was the source in some of the reports; [2],[3] while pin oak leaf galls infested with a pyemotes mite [4] was implicated in another. Booth and Jones in 1952 described the characteristic cutaneous rosy, red wheel surmounted by a vesicle. These lesions, rapidly becomes a pustular due to secondary bacterial infection. [5],[6] In our case, the patient had red papular lesions; some of them having vesicles from which watery fluid came out. Some of the lesions had pustular points. Our case was a sporadic one with no other person suffering from the same type of lesion in that area, which indicate that the patient might have contracted the ecto-parasite outdoors.

Though this parasite causes small outbreaks, [5],[7] yet, isolated sporadic cases are also recorded. [8] Direct proof of the bite and observing the clinical manifestation is required for clinching the etiological diagnosis. But, microscopic size of the mite and painless biting often makes confirmatory diagnosis difficult [5] . Hence in most of the studies, mite could not be found from the lesion. [2],[3].[5],[6],[7],[8] In the present report, though sporadic one, we could find at least one pyemotes female mite on the skin-scrapping sample from the lesion to implicate in the lesion. But environmental sampling could not be done due operational reason. This case illustrates the importance of appropriate laboratory examination for ectoparasites in case of unexplained dermatoses.


Authors are grateful to the anonymous entomology expert of Center for Disease Control, Atlanta who helped us in identifying the mite.


1Butler L, Amrine J, Baniecki J. Review on Straw itch mite (Pyemotes tritici); Beth Massey, WVU Extension Service Agent: Monongalia County; 2000.
2Grob M, Dorn K, Lautenschlager S. Grain mites, A small epidemic caused by Pyemotes species. Hautarzt 1998;49:838-43.
3Betz TG, Davis BL, Fournier PV, Rawlings JA, Elliot LB, Baggett DA. Occupational dermatitis associated with straw itch mites (Pyemotes ventricosus). JAMA 1982;247:2821-3.
4Centers for Disease Control and Prevention (CDC). Outbreak of pruritic rashes associated with mites, Kansas, 2004. MMWR Morb Mortal Wkly Rep 2005;54:952-5.
5Broce AB, Zurek L, Kalisch JA, Brown R, Keith DL, Gordon D, . Pyemotes herfsi (Acari pyemotidae), a mite New to North America as the cause of bite outbreaks. J Med Entomol 2006;43:610-3.
6Booth BH, Jones RW. Epidemiological and clinical study of grain itch. J Am Med Assoc 1952;150:1575-9.
7Letchford J, Strungs I, Farrell D. Pyemotes species strongly implicated in an outbreak of dermatitis in a Queensland Country hospital. Pathology 1994;26:330-2.
8Hewitt M, Barrow GI, Miller DC, Turk SM. A case of Pyemotes dermatitis with a note on the role of these mites in skin disease. Br J Dermatol 1976;94:423-30.