Sed as levocetirizine-induced fixed drug eruption which was confirmed by patch test. She has crossPDE10 Inhibitor Storage & Stability reactions with other piperazine derivatives such as cetirizine and hydroxyzine. We encouraged that the patients steer clear of taking these antihistamines. Fexofenadine may be an alternative drug with no adverse reaction to patient.N O OLorantadineFexofenadine, (R)-typeFig. three. Structures of anti-histamine; piperazine derivatives and piperidine derivatives. Pictures have been extracted from website (en.wikipedia. org).DISCUSSIONLevocetirizine is the single R-isomer of cetirizine dihydrochloride, and has twice on the affinity for the H1-receptor in comparison with cetirizine . The chemical structures have been shown in Fig. 3. Levocetirizine was noted as protected and successful remedy for allergic disease including allergic rhinitis and chronic urticaria . There was a handful of reports of piperazine antihistamine induced delayed hypersensitivity reaction [2-4, 6, 7]. One particular case-series was reported that NK2 Antagonist web hydroxyzine induced fixed drug eruption on the penis in four kids . Rechallenges were carried out and result in the exact same drug eruption . In 2002, Assou e et al.  reported that the hydroxyzine induced the same morphologic cutaneous eruption in the exact same web page which cetirizine had induced drug eruption before. Interestingly, two drugs are piperazine antihistamines. In 2007, Mariana et al reported 1 case of fixed drug eruption to cetirizine . The results of patch test with cetirizine, levocetirizine and hydroxyzine which were all piperazine antihistamines have been positive. These benefits could possibly be evidences apallergy.orgthat delayed sort antihistamine induced hypersensitivity showed cross-reactions in between equivalent chemical structures. Several instances of instant hypersensitivity reactions have been also reported [6, 10, 11]. In 2006, Gonz ez de Olano et al.  reported a cetirizine-induced acute urticaria which was confirmed by oral provocation test, even though the skin prick test was negative. In 2009, a case of cetirizine induced anaphylaxis was reported . Extreme breathlessness, urticarial eruption, loss of consciousness and hypotension had been created within 15 min right after oral ingestion of cetirizine, and recovered just after epinephrine injection. That was the first exposure to the patient, and the mechanism of anaphylaxis induced by cetirizine was unclear . Within the first-generation antihistamines, hydroxyzine, buclizine, cyclizine and meclizine belong to piperazines . Within the second generation antihistamines, cetirizine and levocetirizine belong to piperazines . A zatadine, c yproheptadine, diphennylpyraline and ketotifen belong to piperidines as the first-generation antihistamines, and astemizole, desloratadine, ebastine, fexofenadine, levocabastine, loratadine, mizolastine, olopatadine and terfenadine belong to piperidine as the secondgeneration antihistamines . Within the present case, the patient hasdx.doi.org/10.5415/apallergy.2013.three.four.Asia PacificallergyKim MY, et al.a levocetirizine induced fixed drug eruption, and also the piperazine derivatives which include cetirizine and hydroxyzine showed crossreactions around the patch test. Interestingly, antihistamines that are piperidine derivatives such as ebastine, fexofenadine and loratadine did not show cross-reaction on the patch test. To confirm the security of option candidate drug, oral challenge was performed with fexofenadine. The patient was tolerable even after taking 120 mg fexofenadine for 3 days, and there was no additi.