Preseasonal immunotherapy of ragweed hay fever with the major allergen of ragweed pollen, antigen E, has been tested in double-blind controlled comparisons with whole extract of ragweed and placebos over a period of four years. Antigen E was well tolerated by ragweed-sensitive patients, giving fewer systemic and local reactions than whole extract. As a result, greater quantities of antigen E could be administered in its purified form than could be given in whole extract. Gradually increasing doses of antigen E were given preseasonally each year as this relative safety became apparent. Therapeutic results were significantly better than the results of placebo injections in the third and fourth years of trial when the antigen E-treated patients received an average preseasonal dose of 252 and 743 mcg., respectively. These results were similar to those obtained in patients treated with whole ragweed extract in the same years with average doses of 2,440 and 9,480 PNU, respectively. Whether similar doses can be administered with as good a result in the first year of treatment remains to be tested. It seems likely that a major proportion of the desensitizing effect of whole extract can be attributed to antigen E.
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