Pulmonology · Medical Literature
Association between asthma, allergic rhinitis, atopic dermatitis, and dental caries: evidence from systematic review with meta-analysis and Mendelian randomisation investigation.
Abstract
Allergic diseases and dental caries share overlapping epidemiological trends and risk factors, compromising the patients' quality of life and increasing health care costs. We aimed to explore the associations and potential causal relationships between allergic diseases (asthma, allergic rhinitis, and atopic dermatitis) and the presence/severity of dental caries. We conducted a systematic review and meta-analysis by searching PubMed, Embase, and the Cochrane Library studies published up to 16 June 2025 reporting dental caries outcomes in relation to asthma, allergic rhinitis, or atopic dermatitis. We calculated pooled odds ratios (ORs) and standardised mean differences (SMDs) using random-effects models and utilised meta-regression to investigate heterogeneity. Then, we performed a two-sample Mendelian randomisation (MR) analysis based on genome-wide association study data to assess causal relationships, employing inverse-variance weighted (IVW) and other MR methods. We included 60 studies encompassing 343 975 participants across 22 countries/regions. Asthma (OR = 1.44; 95% CI = 1.17, 1.76) and atopic dermatitis (OR = 1.09; 95% CI = 1.01, 1.17) were associated with an increased risk of dental caries, while allergic rhinitis was not (OR = 1.01; 95% CI = 0.86, 1.18). Asthma and atopic dermatitis patients had higher decayed, missing, and filled teeth for permanent dentition (DMFT) scores, with SMDs of 0.92 (95% CI = 0.32, 1.52) and 0.06 (95% CI = -0.02, 0.14). We also found higher decayed, missing, and filled surfaces for permanent dentition (DMFS) and decayed, extracted, and filled surfaces for primary dentition (defs/dfs) scores in allergic patients, while dmft/dft and the plaque index scores did not show statistically significant associations, with SMDs of 0.17 (95% CI = -0.60, 0.93) and 1.78 (95% CI = -1.47, 5.03), respectively. The MR analysis confirmed a potential causal link for asthma (IVW OR = 1.09; 95% CI = 1.02, 1.17) and a non-significant trend for atopic dermatitis (OR = 1.05; 95% CI = 0.99, 1.11). Our analysis showed that asthma and atopic dermatitis could be associated with an increased risk and severity of dental caries, while allergic rhinitis is not. Clinical practitioners could consider adopting an integrated prevention strategy that addresses the comorbidity between oral health and allergic diseases. PROSPERO: CRD420251103903.
Clinical relevance
Among patients with allergic diseases, do asthma, allergic rhinitis, and atopic dermatitis independently associate with — and potentially cause — increased risk or severity of dental caries? __SNAPSHOT__ {"studyDesign":"Systematic review with meta-analysis (random-effects models) combined with two-sample Mendelian randomisation (MR) analysis using GWAS summary data","setting":"Multinational; literature search of PubMed, Embase, and the Cochrane Library (studies published up to 16 June 2025); 22 countries/regions represented across included studies","sampleSize":"n = 343,975 participants across 60 included studies","population":"Patients with physician- or self-reported asthma, allergic rhinitis, or atopic dermatitis compared to non-allergic controls; age range not reported in abstract; diverse international populations across 22 countries/regions","intervention":"Exposure: presence of allergic disease (asthma, allergic rhinitis, or atopic dermatitis)","comparator":"Non-allergic controls in each included observational study; in the MR component, genetically predicted allergic disease as exposure with dental caries as the outcome","primaryOutcome":"Presence of dental caries (binary: pooled OR) and caries severity via DMFT/DMFS scores for permanent dentition and dmft/dft/defs/dfs scores for primary dentition (continuous: pooled SMD/WMD)","followUp":"Not reported (predominantly cross-sectional studies in the meta-analytic component; MR analysis is inherently cross-sectional in design)","fundingSource":"Not reported in the abstract or retrieved article text"}
Key findings
The meta-analysis of 60 studies (n = 343,975) found that asthma was associated with a statistically significant 44% increased odds of dental caries (OR = 1.44; 95% CI = 1.17–1.76) and atopic dermatitis with a modest 9% increased odds (OR = 1.09; 95% CI = 1.01–1.17). Allergic rhinitis showed no significant association (OR = 1.01; 95% CI = 0.86–1.18). Regarding caries severity, asthma patients had meaningfully higher DMFT scores (SMD = 0.92; 95% CI = 0.32–1.52), suggesting a large effect size on permanent dentition burden, though the atopic dermatitis DMFT difference was minimal (SMD = 0.06; 95% CI = −0.02–0.14, not statistically significant). Higher DMFS and defs/dfs scores were observed in allergic patients overall; dmft/dft (SMD = 0.17; 95% CI = −0.60–0.93) and plaque index (SMD = 1.78; 95% CI = −1.47–5.03) did not reach statistical significance. In the two-sample MR analysis, asthma demonstrated a statistically significant potential causal effect on dental caries (IVW OR = 1.09; 95% CI = 1.02–1.17). For atopic dermatitis, the MR point estimate was directionally consistent (OR = 1.05; 95% CI = 0.99–1.11) but did not reach statistical significance, constituting a non-significant trend only. MR results for allergic rhinitis were not statistically significant. P-values for the primary meta-analytic ORs were not individually reported in the available abstract. NNT/NNH are not calculable from the data reported. Publication bias was identified in the DMFT and dmft/dft results via funnel plot asymmetry and Egger's test.
Practice implications
This study establishes a statistically significant epidemiological association between asthma and dental caries, with an effect size (OR = 1.44) that is clinically plausible given established pathophysiological mechanisms including mouth-breathing, beta-agonist–induced xerostomia, and inhaled corticosteroid use promoting oral Candida and cariogenic flora. The complementary MR analysis provides preliminary genetic-epidemiological evidence that this association may be at least partially causal for asthma (IVW OR = 1.09), though the MR effect size is more modest than the observational estimate, suggesting residual confounding in the observational component. The atopic dermatitis association is statistically significant in the meta-analysis but the effect is small (OR = 1.09) and the MR signal did not reach significance, making causal inference tentative for this condition. Allergic rhinitis showed no meaningful association in either the meta-analysis or MR — a finding that challenges prior conflicting reports attributing caries risk to rhinitis-related mouth breathing. This study cannot establish directionality or mechanism from the observational component alone; MR is limited by the assumption of no horizontal pleiotropy, and the IVW estimates may still be confounded by genetic correlations among atopic conditions. The findings apply most clearly to asthmatic patients across mixed age groups and international settings; pediatric-specific and elderly patients, as well as those by asthma severity or pharmacological regimen (e.g., ICS users), were not analyzed as distinct subgroups in this abstract. Only an abstract and published article web excerpt were available; full sub-group and sensitivity analysis data should be reviewed in the primary publication before clinical application. __LIMITATIONS__ Substantial heterogeneity expected across 60 studies from 22 countries given variability in caries diagnostic criteria, population demographics, and allergic disease ascertainment methods,Publication bias identified in DMFT and dmft/dft analyses by funnel plot and Egger's test, suggesting the pooled estimates may overstate the true association,Most constituent studies are cross-sectional, precluding temporal inference about caries development following allergic disease onset,The MR analysis is based on publicly available GWAS summary data; the specific GWAS datasets, sample sizes, and populations used for the MR component are not fully detailed in available text, limiting independent appraisal,The MR assumes no horizontal pleiotropy and no population stratification — assumptions that are difficult to verify in complex atopic diseases with extensive genetic overlap,The MR effect size for asthma (IVW OR = 1.09) is considerably smaller than the observational OR (1.44), indicating likely residual confounding or effect modification in the observational component,Medication effects (inhaled corticosteroids, antihistamines, beta-agonists) as mediators or confounders were not isolated in the analysis,Caries outcomes are composite indices (DMFT/DMFS) that aggregate decayed, missing, and filled teeth — limiting insight into active caries burden versus historical dental treatment,Funding source not reported, preventing assessment of potential sponsorship bias,Generalizability to populations of non-European ancestry may be limited depending on the GWAS datasets employed in the MR component __BOTTOM_LINE_CATEGORY__ potentially_practice_informing __BOTTOM_LINE__ This large systematic review and meta-analysis, supported by Mendelian randomisation, provides the strongest epidemiological evidence to date that asthma is associated with — and potentially causally linked to — increased dental caries risk and severity; atopic dermatitis shows a small but significant observational association without confirmed genetic causality, and allergic rhinitis does not appear to be independently associated. Clinicians managing asthmatic patients — particularly pulmonologists, allergists, and primary care providers — should be aware of this bidirectional oral-respiratory disease burden and consider incorporating routine dental health counselling and appropriate referral into asthma management plans. This evidence is hypothesis-generating for atopic dermatitis and insufficient to change practice for allergic rhinitis, and prospective studies accounting for specific medications and asthma severity are needed to refine risk stratification.