Acyclovir allergies are considered rare. According to Drug Patent Watch, allergic reactions to acyclovir are infrequent [1]. The National Center for Biotechnology Information also notes that hypersensitivity reactions to acyclovir are rare, occurring in less than 1% of patients [2]. WebMD further supports this, stating that serious allergic reactions to acyclovir are uncommon [3]. Overall, while allergic reactions to acyclovir can occur, they are not a common occurrence based on the sources provided.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/ACYCLOVIR
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6232537/
[3] https://www.webmd.com/drugs/2/drug-941/acyclovir-oral/details