Perfluoroalkyl and polyfluoroalkyl substances (PFASs), as a group of persistent organic pollutants among environmental endocrine disruptors, are widely used in industrial production and daily life. PFASs are widely and persistently present in the environment and organisms due to their bioaccumulation, long half-life, and low degradability properties. Published studies have proved that PFASs have immunotoxicity, endocrine toxicity, neurotoxicity, reproductive toxicity, and hepatotoxicity. At present, several epidemiological studies have been conducted on the effects of PFASs on allergic diseases, the research endpoints include asthma, allergic rhinitis, atopic dermatitis, and the expression of allergic biomarkers such as serum immunoglobulin E (IgE), but no consistent results have been observed yet. PFASs have the potential to activate several signaling pathways, including the peroxisome proliferator-activated receptor (PPAR), nuclear factor-κB (NF-κB), and JAK/STAT pathways. These mechanisms, along with increasing mast cell calcium influx and sex hormone synergistic effects, may contribute to immunomodulation in allergic diseases. At present, the exact human effect of PFASs exposure on allergic diseases and the related mechanisms are still uncertain. This review focused on the impacts of PFASs on asthma, allergic rhinitis, and atopic dermatitis and their possible mechanisms, so as to provide research ideas for the prevention, diagnosis, and treatment of allergic diseases.