Chemical materials can be irritant.
Chemische Stoffe koennen reizend sein.

e.g.
Einstufung und Kennzeichnung nach Gefahrstoffverordnung (Gefahr Stoff Verordnung vom 01.01.2003)
The chemical abbreviations:
T+ = sehr giftig
T = giftig und / oder krebserzeugend, fortpflanzungsgefährdend, erbgutverändernd
C = ätzend
Xi = reizend
Xn = gesundheitsschädlich
S = sensibilisierende Eigenschaften
H = hautresorptiv
E = explosionsgefährlich
O = brandfördernd
F+ = hochentzündlich
F = leichtentzündlich
N = umweltgefährlich
could be added to their respective words.
And likewise the same thing in English (European Standard)
TX= Very Toxic
T = Toxic
CX = Highly Corrosive
CAN = Known or Suspected Carcinogen
C = Corrosive
X = Harmful
XI = Irritant
S = Allergen or Sensitizer
V = Low Toxicity
http://www.chemrest.com/German/Toxicity and Risk Codes/Epichlorohydrin.htm
http://de.wikipedia.org/wiki/Reizend

Until now, LEO does not have any chemical reference under "reizend", and irritant is (also correctly) translated with "aufreizend".
Should be added.

If this is not added, fun like the following will continue :)
http://www.wizdforums.co.uk/showthread.php?t=...
"I've got a bottle here and all it has on is the hazardous substance sign (black cross in an orange square) Undearneath it has written "reizend" which translates to charmingly apparently"