CRITICAL bcs allergy: Do I need to permanently caulk or seal any obvious cracks/openings before or after spraying them ?

”Focus on cracks in hardwood floors, and crevices around baseboards. It can be beneficial to permanently caulk or seal any obvious cracks or openings.” FleaScience
Hi Adam 🙂 ! 
I would think that it would be logical to first spray and close. On the other hand closing and spraying afterward everywhere makes more sense for me as it will (unless  I am wrong) ensure a more systematic result (in case I miss some openings). 
Adam, I had a very severe allergic reaction to fleas’ bites (many huge blisters, swelling, etc.). If you’re ever interested I would be happy to share what happened to me and email you pictures so you would have (in case you don’t) an example of an extreme case of allergy to flea’s bites.  
The precious and serious information you provide in fleascience helped me first keep calm despite a very high level of anxiety\despair and see clearly what I needed to do in a brilliant integrated approach that made sense to me much more than what those exterminators companies pretended (most of them often ignorant of basing information about fleas’ behavior – as I would discover later).
I absolutely needed to know the nature of the beast before addressing the issue in an efficient manner. After all, good solutions depend on good data, right?  And you provided me with good data and ….solutions.
Taking into account my condition I cannot afford not to do my best to never ever go through the hell I went through before finally, I could pinpoint the origin of my nightmare.
On the other hand, thanks to your site, I discovered how nature could build up awesome tiny little creatures perfectly programmed to do their job and survive. Absolutely fascinating despite what I went through.
Merci mille fois (in French 🙂 (thank you a thousand time)
Micheline
Montreal, Quebec