Agave americana (Figure 1) is a popular ornamental plant. Irritant contact dermatitis induced by Agave americana has rarely been reported.
We present a case of allergic contact dermatitis associated with the use of this plant.
A 58 year-old woman developed an acute dermatitis on her face and neck after application of Agave americana. Due to confusion she had used this plant as a treatment for rheumatism instead of Aloe vera. A few minutes after using this plant she developed an intense pruritus on the contact zone. This area was intensive washed with water and soap. Twelve hours later she developed erythema, pruritus, oedema and suppurative lesions on her face and neck. The symptoms disappeared after treatment with systemic antihistamines and corticosteroids some weeks later.
Patch testing was carried out according to the International Contact Dermatitis Research Group recommendations with a European Standard Battery and a European Plants Battery.
An open test (sap was applied on the wrist) with Agave americana, and then an open test with the plant sap in dilution (2g was dissolved in 2ml of saline solution, and 1/10 and 1/100 of this dilution) was carried out in the patient and in five controls.
The patch tests were positive at 48 and 96hours to nickel sulphate and negative to any other allergens tested. The open test on the patient was intensive positive. A few minutes after the first contact on the wrist, she developed pruritus, erythema, papules and oedema. Treatment with occlusion topical corticosteroids was recommended. The open test on controls was mild positive; immediate pruritus with some late papules without pruritus were presented in two of them. The open test with the plant sap in dilution was negative in the patient and in the controls to all concentrations.
Agave americana belongs to the Agaveceae family1 and is widely used in ornamental gardens in the Mediterranean area. The species of Agave americana have irritant properties due to the presence of calcium oxalate crystals (raphides),2 volatile oil, saponins, agave gum and other components in its sap.3 Calcium oxalate crystals seem to be the irritant main component.4 In some case systemic symptoms have been described.5
Due to the mild irritant reaction observed in the controls, compared with the severe reaction in the patient we diagnosed this case as allergic contact dermatitis. Probably the previous contact causing sensitivity could have been caused when the patient pruned the plant.
Because of the onset of symptoms, which appeared in the morning and the patient had used the plant at night, photodermatitis was ruled out. A nickel sulphate contact allergy without present relevance was diagnosed.
Our patient had an important local reaction with open test. Due to the potential of plants to cause severe dermatitis, physicians should be careful with the use of plants for the diagnosis of phytodermatitis. To the best of our knowledge we recommend that in case of unknown products an open test must be the first procedure, and when this open test is negative, a patch test will be performed.
