This does not sound like allergies.  Chronic allergies are not sudden onset respiratory difficult that then goes away.  Most canine allergies present in the form of skin issues--itching, scratching, and redness.  Respiratory difficulty can be seen when dogs have anaphylactic shock--a sudden, severe reaction to an environmental stimuli.  This can result in cardio-respiratory collapse and also does not resolve on its own.  This can be life threatening--like a person with a serious reaction to bees.
Respiratory difficulty can be due to primary lung pathology or heart disease.  I am wondering if your dog is having syncopal episodes.  This is where a heart problem like a severe arrhythmia can lead to weakness, lack of blood flow, decreased oxygenation, weakness, and collapse.
It would be best to have your dog examined by a veterinarian to rule out any serious conditions leading to these signs.

 He might have allergy with particular type of herb or there can be a sensitive bronchi in it. It can be done like if he takes  a long race and then water percentage gets lowered .It is suggestible to go to a vet so that it can be seen and diagnosed properly otherwise the problem can increase even.

 He can have allergies!  Is he over weight?  Sometimes strenuous activity on an over-weight animal can cause strain on the lungs.  Do you have a lot of flowers in your yard?  A lot of flowers and plants are poisonous to our animals.  For instance Tulips, can be deadly,  Rhododendrons, even green house plants, all if ingested.  I was unaware of this until about two years ago, one of my Labradors eyes kept running and the vet asked me what type of flowers I had around and plants, and I didn't believe it, it sounded absurd until I researched it myself online.  Good-Luck