Glochids of Opuntia
The areoles of Opuntia microdasys (Fig. a) are an order of magnitude smaller than those of Trichocereus candicans, and to the naked eye, less intimidating - looking rather like spots of brown fur. However, very close examination shows that the innocuous looking brown 'fur' is actually made up of glochids. Each areole bears around 30 - 40 of them: they are sharp, brittle and above all, barbed (Fig. b).
It is the small barbs near the tip of the glochid (arrow in Fig. b) which cause the problems. The sharp glochid penetrates your skin, and the barbs anchor it firmly. Because glochids are brittle, the larger part of the shaft breaks off easily, leaving the tip stubbornly embedded, and virtually impossible to get out. In addition, the thickness of the tips - less than 30 ยต - makes them invisible without a microscope, so you only become aware of them when they start to itch. The more you rub and scratch your itching skin, the more deeply and firmly the glochid tips become embedded. The only solution at this stage is to stop scratching and wait; they will eventually fall out of their own accord. Washing the skin in hot soapy water sometimes helps.
A better option is not to get them into your skin in the first place. Wear rubberised gloves when handling Opuntias, keep your hands away from your face (a glochid in the eye would be very unpleasant) and wash the gloves before you take them off.
