OBJECTIVE To investigate whether there is an association between suicidal ideation (SI) and allergic diseases in adults. METHODS This was a comparative cross-sectional study involving individuals ranging from 20 to 50 years of age recruited from a university hospital in the city of Guadalajara, Mexico. We included patients with a confirmed diagnosis of allergic asthma, those with a confirmed diagnosis of allergic rhinitis, and healthy controls. All subjects completed the Beck Depression Inventory-II (BDI-II), which includes an item that evaluates the presence of suicidal thoughts or desires within the last two weeks, in order to identify SI. RESULTS The sample comprised 115 patients with allergic asthma, 111 patients with allergic rhinitis, and 96 healthy controls. The number of individuals identified with SI in the three groups were, respectively, 17 (14.8%), 13 (11.7%), and 8 (8.3%). Regarding the presence of SI, no statistically significant association was found in the allergic asthma group (OR = 1.98; 95% CI: 0.78-4.64; p = 0.154) or in the allergic rhinitis group (OR = 1.46; 95% CI: 0.58-3.68; p = 0.424) when they were compared with the control group. However, the presence of depression was associated with SI in the three groups: allergic asthma (OR = 12.36; 95% CI: 2.67-57.15; p = 0.001); allergic rhinitis (OR = 6.20; 95% CI: 1.66-23.14; p = 0.006); and control (OR = 21.0; 95% CI: 3.75-117.36; p < 0,001). CONCLUSIONS In comparison with the control group, no association was found between SI and the groups with allergic diseases. In contrast, there was association between SI and depression in the three groups.