1. An allergic reaction that becomes apparent only hours after contact
   - delayed allergy

Type of: allergic reaction, allergy

• genus Oleandra
• genus Olearia
• genus Olfersia
• genus Oligoplites
• genus Oligoporus
• genus Ommastrephes
• genus Omphalotus
• genus Oncidium
• genus Oncorhynchus
• genus Ondatra
• genus Oniscus
• genus Onobrychis
• genus Onoclea
• genus Ononis
• genus Onopordon
• genus Onopordum
• genus Onosmodium
• genus Onychium
• genus Onychogalea
• genus Onychomys
• genus Opheodrys
• genus Ophiodon
• genus Ophioglossum
• genus Ophiophagus
• genus Ophisaurus