Inhaled allergen challenge of subjects with allergic asthma allows the study of mechanisms involved in allergen-induced airway inflammation. The objective of this study was to identify changes in the plasma proteome associated with a late phase response (LPR) causing airway obstruction occurring 4-8 hours after the initial early response. Serial plasma samples from asthmatics undergoing inhaled allergen challenge were analyzed. Mass spectrometry data was analyzed using a linear regression to model the relationship between the degree of airway obstruction during the LPR and plasma proteome changes evoked by the inhaled allergen challenge. Inhaled allergen challenge induced changes in the plasma proteome including upregulation of the protease inhibitors alpha-1-antitrypsin, alpha-1-antichymotrypsin and plasma serine protease inhibitor. Out of 396 quantified proteins, 150 showed a statistically significant change 23 hours post allergen challenge. Further proteomic changes were associated with the LPR, including altered levels of coagulation factors such as an increased factor XII A and a decreased von Willebrand factor. Allergic reactions to inhaled allergens in asthmatic subjects was associated with changes in a large proportion of the measured plasma proteome, whereof protease inhibitors show the largest changes, likely to influence the inflammatory response. Of several other proteins altered in relation to the LPR, many are associated with coagulation.