Lorraine wrote
> We have been harvesting lachenalia and a number of other kinds
> of spring flowering bulbs,... We've nearly been driven mad with
> itchy skin and itchy lumps/welts, even on those parts of the
> body which are covered by clothes.... we need to find a way to
> protect ourselves and our workers from being adversely affected
> by what we've been told are Calcium oxalate raphides
> (needle-like, microscopic calcium crystals).
Your experience does not sound right for calcium oxalate. Itchy lumps and welts suggest
an allergic reaction to something. I would guess something other than the Lachenalia is
causing the trouble. Calcium oxalate is carried in the sap and would only affect parts
of the body directly exposed to the sap, either directly from the plant or transferred
from the hands to the other body parts. In addition, most adult gardeners have
sufficiently tough skin on our hands that calcium oxalate crystals should cause little
trouble. I have never had any skin reactions after handling Lachenalia nor aroids such
as Caladium and Dieffenbachia, which are known for having calcium oxalate in the sap.
I am not familiar with Australian flora nor fauna that might cause allergic reactions;
you might contact other Australian gardeners to see whether this is a recognized
problem. Immune reactions are caused by antibodies, present in the person, directed
against a particular foreign substance such as a protein from another organism.
Reactions may occur in parts of the body not directly exposed to the substance because
antibodies and white blood cells involved in the immune reactions are carried in the
blood. Several species of Rhus ("poison ivy, poison sumac") present in the US are famous
for causing such reactions. Immune reactions generally do not occur on the first
exposure to the substance because the body needs to become sensitized after the first
exposure and produce antibodies, which takes some time.
Leo Martin
Phoenix Arizona USA