I've inherited dodgy sinuses from my mum which are always getting infected (it swells up until it feels like there's a potato stuck up my nose, or that thing Arnie pulled out in the original Total Recall film), and I also get post nasal drip. I hate that nasty acidic mucus that's constantly running down the back of my thoat, making it really sore, and I just know it's going to turn into a horrible wheezy cough once it gets to the bubbling-in-my-lungs-every-time-I-breathe-out stage.
All that over the counter remedies are doing is treating the symptoms, and the problem is that the cause is either a virus or bacteria, one of which can't be treated outright, and the other of which needs anti-biotics. You're not going to get them without a prescription, and you're not going to get a prescription for a runny nose and a cough.
Here's how I tackle it:
1. Cut out all dairy from my diet. Milk, cheese, butter, yoghurt and ice cream. Dairy makes your body produce more and thicker mucus, on top of what it's producing to try and flush away what's going on in your sinuses. Problem is, a lot of things actually like living in mucus (the dairy can also cause spots. If I eat a lot in a short time, I just know I'm going to have a break out).
2. While you can't get anti-biotics, there are still things you can take that help fight infections (bacterial or viral), alongside what your body is trying to do. Green tea is something you can drink pretty much all the time to keep everything at a lower background level (to make it properly let the water cool for a couple of minutes before putting the bag in it). Echinacea is something you can start taking as soon as you feel anything cold or flu like coming on, and can help beat things faster, so something you would of had for several days can be over in just one. Same goes for Pau d'arco, which is the bark of a Brazilian rainforest tree, it's pretty good at helping you fight off infections (if you think about it, rainforests are hot and humid, bacteria and fungi grow like crazy in hot and humid conditions, so this tree has stuff in its bark to limit the growth of fungus and bacteria).
3. To handle the nasty sore throat, there's always the old reliable ginger, honey and lemon juice (honey being another anti-bacterial). I also drink tea with liquorice or cloves in, as they both soothe the sore throat (I even used to chew cloves when my wisdom teeth were coming through, because they're a natural painkiller).
4. Breathe steam. It helps losen up the mucus and flush out your sinuses (I remember Gomez Adams from the old black and white TV show, sitting holding his head over a bowl of steaming water, covered in a towel, when he had a bad cold). This is probably partly why chicken soup, or other soups are recommended for colds, healthy food and nostrils flushed with steam at the same time. Food containing black pepper, mustard, horseradish or chilli will also help flush out your sinuses and help your immune system (they all improve blood circulation). I always go overboard with the black pepper in soup, or I just make Szechuan hot and sour soup, which is basically a spicy tomato soup. If I've got my head over a bowl of steaming hot water, I'll add black pepper essential oil to it to help clear my sinuses, or just add it to a hot bath.
Basically the whole idea is to strengthen your immune system instead of weakening it (what the typical western diet does), so you can fight off an infection in a couple of days, instead of a week.
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