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As advice, I often give by telephone to patients with sinusitis to use a mustard foot bath.[because most people have mustard at hand]
Take more or less 4 teaspoons of mustard seeds-crush them- to one liter of hot water.
[you can, of course, change the proportions]
After a few minutes put your feet in the bucket or so.
Dependent on the room temperature dry the feet after some 15 minutes or when you feel they get red.
You can repeat this if useful a few times per day for a few days.
Drinking kohlrabi juice -one or two cups per day mixed with some carrot juice for 2-3 days is another advice as well as eating horseradish “homemade”, available in most super sols and minimarkets].
Of course, there are many more possibilities. Food advice will be known by most patients already, I hope!
Antibiotics are rarely of any benefit in sinusitis.[and if any, then doxycycline but not in pregnancy]

As homeopathy one can try [also during pregnancy]

kal.bichrom. /pulsatilla /mercur. sol /hepar sulphur/hydrastis/  collinsonia D6 aa 5 cc/  portulaca M.T 10 cc /thymi M.T 10cc  suck from a teaspoon twice per day 5 drops and take another 15 drops thereafter in some water.