Careless weed
Clinical Relevance
IgE-mediated reactions
Anecdotal evidence suggests that asthma, allergic rhinitis and allergic conjunctivitis are common following exposure to pollen from Careless weed; however, few specific studies have been reported to date.
Sensitization to Careless weed has been documented in Tucson, Arizona and in Mexico. In a Mexican study of allergic patients, sensitization to Careless weed was demonstrated in 43.8%.
In a study examining aeroallergen sensitization rates in military children in Texas undergoing skin testing for rhinitis, of 209 patients, 27% were sensitized to Common Pigweed or Careless weed.
In a study in the Midwestern USA, evaluating the frequency of sensitization to cannabis pollen, found that 61% were skin prick positive for cannabis and all subjects were also skin test positive to weeds pollinating during the same period: Ragweed, Pigweed, Cocklebur, Russian thistle, Marsh elder, and Kochia.
In a study among Thai patients with vernal keratoconjunctivitis, positive results of skin prick testing to Acacia, Careless weed, mold, Johnson grass and Cow's milk were significantly more common in patients with palpebral VKC.
Cross-Reactivity
Cross-reactivity could be expected between species of the family Amaranthaceae, and in particular the genus Amaranthus.
Although no specific information on cross-reactivity of this plant with others exists, a high degree of cross reactivity has been reported to occur between Goosefoot (Chenopodium album) and Saltwort (Salsola kali), and other species taxonomically less related members of the Amaranthaceae family like Amaranthus retroflexus. Common allergenic determinants are present in these plants.
In a study using a fluorescent allergosorbent test, similar antigenic determinants were found between Short Ragweed and Giant Ragweed, Cocklebur, Lamb's Quarters, Rough Pigweed, Marsh Elder, and Goldenrod. Cocklebur and Giant Ragweed were highly potent in competitively binding to short ragweed IgE. The other pollens demonstrated lower potency of cross-reacting antigens.
References
- palmeri. VTWIGPAA. http://www.ppws.vt.edu/scott/weed_id/amapa.html 2011 [cited 2011].
- Calabria CW, Dice J. Aeroallergen sensitization rates in military children with rhinitis symptoms. Ann Allergy Asthma Immunol. 2007;99(2):161-9.
- Gómez Castillo CA, Martínez Cairo Cueto S. [Diagnostic use of enzymatic RAST skin tests and determination of eosinophils in nasal mucosa in allergic rhinitis]. Rev Alerg Mex. 1998;45(6):150-8.
- Ortega EV, Vázquez MI, Tapia JG, Feria AJ. [Most common allergens in allergic patients admitted into a third-level hospital]. Rev Alerg Mex. 2004;51(4):145-50.
- Stern DA, Lohman IC, Wright AL, Taussig LM, Martinez FD, Halonen M. Dynamic changes in sensitization to specific aeroallergens in children raised in a desert environment. Clinical and experimental allergy : journal of the British Society for Allergy and Clinical Immunology. 2004;34(10):1563-669.
- Stokes JR, Hartel R, Ford LB, Casale TB. Cannabis (hemp) positive skin tests and respiratory symptoms. Ann Allergy Asthma Immunol. 2000;85(3):238-40.
- Kosrirukvongs P, Vichyanond P, Wongsawad W. Vernal keratoconjunctivitis in Thailand. Asian Pacific journal of allergy and immunology. 2003;21(1):25-30.