In this study, we took opportunity of a survey to conduct an analysis in the subsample restricted to those with asthma symptoms and explored the relationship between several potential risk factors to poorly controlled asthma. The main findings of this study were: (i) 50.0% of children with a history of wheezing in the last 12 months had symptoms of greater severity and/or at least one hospitalisation of asthma, and were considered poorly controlled; (ii) the presence of eczema alone or in conjunction with rhinitis was associated with asthma of poor control; (iii) the presence of mould in the house was inversely associated with poorly controlled asthma.
Eczema has been previously associated with asthma severity, including one study in Brazil 
. In another report, bronchial hyperresponsiveness and eosinophilic airway inflammation were significantly more common in patients with moderate to severe eczema, especially those with positive SPT and high levels of IgE, than in control subjects without eczema 
. The authors argue that eosinophils activated in eczema might contribute to airway inflammation in these patients. In our study, however surprisingly we found no association between atopy and flexural skin lesions, but the association between flexural skin lesions and severe asthma remained even after controlling for atopy. These results reinforce the concept of multicausality of eczema, and stresses the possibility that asthma and eczema may share other mechanisms beyond atopy.
The association between indoor mould exposure and asthma has been described in several studies, but few studies analysed the association between mould and asthma severity or control. Indeed, there is some evidence that sensitisation and exposure to certain moulds is associated with asthma exacerbations, which is related to control. In a study in Australia, asthmatic children with sensitisation to Alternaria sp
had more symptoms and used more often bronchodilator than those without sensitisation 
. If mould exposure triggers symptoms of asthma, it should be associated with severity among subjects who are sensitized. But there are no consistent reports on this aspect in the literature: a case-control study based on 763 children in the UK, which used the criteria of the ISAAC questionnaire to define asthma severity, did not find an association between mould exposure and asthma severity 
. In our study, the presence of indoor mould exposure was assessed by inspection by the interviewer and was significantly inversely associated with poor control of asthma. We speculate that this finding could be due to reverse causation: the guardians of asthmatic children with poorly controlled asthma would take more actions to remove mould from the homes or move away from homes with mould, assuming guardians were concerned with mould. We questioned about the presence of mould at home in a second survey of the same population conducted in 2007 and we observed a significant reduction of mould in homes of wheezing children. However, further studies are needed to prove that the removal of mould reduces the severity of asthma in this population. Finally, mould was found during home inspection in 72% of the 374 children, but only 5 children (1.33%) were found sensitised to the fungi allergens used in our SPTs.
In order to evaluate the relationship between rhinitis and eczema with the severity of asthma, we analyzed the risk of asthma of poor control related to either one of them or both combined, in comparison to that of subjects with neither rhinitis nor eczema and found a significantly higher proportion for poorly controlled asthma among children with one of both (rhinitis and eczema) and the highest proportion among children who had both. Applying the ISAAC questionnaire, Solé et al reported the association of rhinitis or eczema and the severity of asthma 
. In our study, the proportion of atopy was not higher among asthmatics with rhinitis and eczema, as compared with those without these comorbities. Therefore atopy could not explain the association described. Further research is needed to determine if the effect of eczema on asthma control is independent of atopy.
For the correct interpretation of our results, one should consider that we did not use data from medical records nor any complementary test at the moment of the survey, such as spirometry. Instead, we analysed self-reported data and thus they are susceptible to misclassification. Given that there have been doubts on the accuracy of the common definition of asthma and its control based on self reported symptoms 
, we have tried to minimise such a bias by using a second and more accurate definition for asthma and two criteria for poor control. It is worth noting that different definitions for asthma control have been used in the literature 
, and along with different interpretations of the questions due to language variation, what makes comparison of results more difficult. This is a population-based study. The sample size for children having asthma (374 out of 1445 surveyed) offer limited power for certain inferences indeed. However, we have a community survey among children with abundant information on potential risk factors, protection factors and outcomes, which are crucial for a more accurate assessment of confounders and consider our methods to be the major strength of this report. In exploring this complex issue, only a few studies 
have managed to perform a comprehensive evaluation of a population-based sample to include multiple potential risk and protection factors.
In conclusion, we identified that eczema increases significantly the chance of poorly controlled asthma among asthmatic children identified in a population survey in a low-income setting. Subjects presenting eczema and concomitant symptoms of rhinitis have a further increase in the risk of poor control of their asthma as compared with individuals having asthma but none of these potential risk factors. This observation adds epidemiological evidence to the hypothesis that asthma and eczema may be related by other mechanisms than atopy.