Fine particulate matter (PM2.5) and ozone (O3) may exert oxidative damage in the nose, which is hypothesized to be associated with worsened asthma symptoms. This study, hence, is to explore whether an oxidative stress biomarker, malondialdehyde (MDA) in the nasal fluid, has the potential to aid personalized asthma control. In a panel study of 43 asthmatic children 5-13 years old, each child was measured 4 times with a 2-week interval between the consecutive clinic visits. At each visit, nasal fluid and urine samples were collected and fractional exhaled nitric oxide (FeNO) was measured as a biomarker of pulmonary inflammation. In addition to nasal MDA, urinary MDA and 8-hydroxy-2′-deoxyguanosine (8-OHdG) were measured as biomarkers of systemic oxidative stress. We also assessed asthma symptoms using the Childhood Asthma-Control Test (C-ACT). We found that IQR increases in 24-hour average personal PM2.5 exposure (22.2 to 33.5 μg/m3), estimated zero to five days prior to a clinic visit, were associated with increased nasal MDA concentrations by 38.6% to 54.9%. Similarly, 24-hour average O3 exposure (7.7 to 8.2 ppb) measured two to four days prior were associated with increased nasal MDA by 22.1% to 69.4%. Only increased PM2.5 exposure was associated with increased FeNO. Increased nasal MDA concentration was associated with decreased total and individual C-ACT scores indicating worsening of asthma symptoms. However, no significant associations were observed between urinary MDA or 8-OHdG and C-ACT scores. The results confirm that oxidative stress plays an important role in linking air pollution exposure and adverse respiratory health effects. These findings support that MDA in the nasal fluid may serve as a useful biomarker for monitoring asthma status, especially in relation to PM2.5 and O3 exposure, two known risk factors of asthma exacerbation.