Animals suffering from atopy or other hypersensitivity disorders frequently receive anti-inflammatory or antipruritic medications and there may be concern that such drugs could influence the results or interpretation of specific tests for IgE. In 2013 Thierry Olivry and Manolis Saridomichelakis, on behalf of the International Committee on Atopic Diseases of Animals, produced evidence based guidelines for anti-allergic drug withdrawal times:
Summary of optimal (OWT) and minimal withdrawal times (MWT) before intradermal and serological tests in dogs
| Drug example | OWT | MWT | |
| Intradermal tests* | |||
| Antihistamines (oral) | Hydroxyzine, cetirizine | 7 | 2 |
| Glucocorticoids (short acting, oral) | Prednisone, prednisolone | 14 | Unknown |
| Glucocorticoids (long acting, injectable) | Methylprednisolone acetate | Unknown | 28 |
| Glucocorticoids (topical) | Hydrocortisone, triamcinolone | 14 (high potency) | 0 (low potency) |
| Glucocorticoids (otic) | Betamethasone, mometasone | 14 | Unknown |
| Ciclosporin (oral) | Ciclosporin | 0 | 0 |
| Tacrolimus | Tacrolimus | 0 | 0 |
| Pentoxifylline (oral) | Pentoxifylline | 0 | 0 |
| Ketoconazole (oral) | ketoconazole | 0 | 0 |
| Essential fatty acids (oral) | Essential fatty acids (various) | 0 | 0 |
| IgE serological tests | |||
| Antihistamines (oral) | Not tested | Unknown | 0 |
| Glucocorticoids (short acting, oral) | Prednisone, prednisolone | 0 | 0 |
| Glucocorticoids (long acting, injectable) | Methylprednisolone acetate | <28 | Unknown |
| Glucocorticoids (topical or otic) | Not tested | Unknown | 0 |
| Ciclosporin (oral) | Ciclosporin | 0 | 0 |
*For intradermal tests, withdrawal times mentioned are those for the determination of the immediate phase reactions.
Optimal withdrawal times (OWT’s) are those that have been shown, or are very likely based on mechanism of action, to be associated with no interference on test results.
Minimal withdrawal times (MWT’s), which are shorter than OWT’s are defined as those that might, at most, be associated with a small inhibitory effect that should not affect the interpretation of most test results.
The effect of type 1 antihistamines on serological testing has not been studied; in theory blockade of the type 1 antihistamine receptor should not impact on the measurement of IgE in patient serum and no withdrawal time is required.
Study data was based on use of oral corticosteroids at anti-inflammatory/antipruritic rather than immunosuppressive doses; therapy for up to 2 months was found to be unlikely to affect serological testing and required no withdrawal period. Extrapolating from this data it has been proposed that use of topical or otic corticosteroids should also not incur any withdrawal period.
The duration of Ciclosporin studies was 6-8 weeks; when used at doses recommended for atopic dermatitis this did not affect serological testing and no withdrawal period is required. The effects of longer courses of ciclosporin on serum IgE levels are unknown. Anecdotally we have experience of a small numbers of cases where prolonged therapy appears to have suppressed the IgE response. In the absence of specific data, it may be prudent to delay testing animals that have been on medication for more than 8 weeks until therapy has been withdrawn for 4-6 weeks.