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April 24, 2005

Comments

Patia

I have heard that's quite common. A pregnant friend once had the same complaint. She said she could hardly bear to go outside. I think it's your body's way of keeping you away from potentially toxic things. Because anything you breathe, your baby breathes.

Jim

I had lunch today with a woman who just had a baby, and asked her if she had experienced an enhanced sense of smell during pregnancy. She groaned and said she had. She didn't know why, but suggested that pregnancy causes an enhancement of almost all the senses. I looked on Google for a cause and couldn't find one, but I did notice that the enhanced sense of smell during pregnancy is often associated with a "craving" for certain smells.

That caught my attention, because for the last month or so I seem to have had a craving for certain smells. It's not as if I identify a smell and go looking for it--that is, I don't wake up and say, well today I need to find, say, some creosote and smell it. But if I go someplace where there are some distinctive odors--such as a hardware store, or a hobby shop--I am reluctant to leave until I'd had a good sniff.

I have assumed sadly that this must result from some terminal stage of idiocy on my part, but I guess that would be better for me than being pregnant.

Jonathan

As a future board-certified Otolaryngologist (we used to be called OtoRHINOlaryngologists, but that was just silly), I can officially state to you that no one, NO ONE, knows why this happens. It most certainly is connected to the same pathways as the increased taste/gag reception from the oral cavity, and is certainly mediated through increased estrogen and hormone balance. These pathways are directly linked to the limbic system in the brain, and are therefore linked to strong emotional and protective reflexes. The olfactory tract has direct input to the limbic system and the brainstem, leading to reflex vomitting in the event of exposure to toxic substances. Thus the "hurl reflex" when you go to an autopsy. I suspect that Tony's instinct that this is evolutionarily preserved is probably right, but how it actually happens is up to anyone to guess. In the end, the senses of smell and taste are by far the least understood senses, and therefore the most interesting.

I think that it's unlikely that the nose actually "smells better". You only have so many olfactory receptors, and the odorant molecules around you aren't likely getting there any easier or faster - in fact, if anything they're getting their slower (see below). So it's likely that estrogen (or some other pregnancy-related hormone or substrate) enhances the perception of smell, or more specifically the limbic activity associated with smell. I have no data to prove this, but it sure sounds sweet.

It is possible that the mucous layer in the nasal passages is somehow thinner or more lipid-soluble in pregnant women. Cervical mucous changes during pregnancy, so nasal mucous may as well. All odorant molecules are similarly lipid soluble, and it is the lipid solubility of a specific compound that confers it's smell intensity. Again, no data to prove this. Just speculation.

Often in the later stages of pregnancy women have really stuffed up noses, making it almost impossible to smell. Estrogen causes hypertrophy of the nasal mucosa, basically blocking off your nasal passages and your sense of smell. So maybe you'll get lucky and have that happen.

And BTW, my wife highly recommends the Arby's Big Roast Beef sandwich to pregnant women everywhere. It's got the cure for what ails ya.

caroline

hey. i was looking around for answers to this just as you and came upon your blog which is a very helpful introduction to the non-neuroendocrinologist. I prawled the abstracts of scientific papers on NIH and came up with this:

----------------------------
Mothers with higher cortisol levels were also better able to recognize their own infants' odors. While cortisol was not related to attitudinal measures of maternal responsiveness, mothers with more prior experience interacting with infants exhibited both more attraction to infant odors and more positive maternal attitudes.
------------------------------
Failure to form this olfactory memory results in the stud [mouse] male being treated as strange, and hence, his pheromones block pregnancy. The results show that a single prolonged exposure to the male during mating forms a life-long olfactory memory trace unless pregnancy ensues. In the event of pregnancy the olfactory memory fades significantly faster, an effect which can be replicated by implants of oestradiol in non-pregnant females. Anatomical studies indicate that neurogenesis of the vomeronasal receptors is enhanced during pregnancy, an event which we interpret as being important for the duration of this olfactory memory.
------------------------------

caroline

however, i disagree with jonathan above on his account of the receptor number being static. neurogenesis occurs in the adult rodent brain and these migrate down to, you guessed it, the olfactory bulb. I wonder if the same neurogenesis occurs in female humans in response to heightened cortisol/oestrogen/[some hormonal molotov cocktail equivalent to pre-giving birth] levels and a potential need to survey the surroundings for danger. thus women develop quick differentiation of neuronal stem cells during pegnancy, providing them with superpowers to protect themselves and their small ones to be. just a morning guess.

Jonathan

Caroline, you may be absolutely right. I just don't know of any human data that demonstrates increased olfactory neuron formation in response to hormone fluctuation. Most patients that we see in clinic that lose their smell (anosmia) through trauma or viral infections never get it back, although we may be skewed in that we only see the ones with the problems. An interesting topic, nonetheless. If this is true, I think you'd also expect to see women on estrogen replacement or oral contraceptives also experience increased olfactory function. Don't know if that's ever been shown. There appears to be data showing that women lose olfactory function during menopause, which is the reverse of this concept.

Interestingly, one of the main initial physical findings (perhaps the first) in Alzheimer's disease is anosmia. A parallel area of research to this topic.

A quick review of relevant literature shows that there is a study going on at the U of Pennsylvania studying the effect of hormone replacement therapy and menopause on olfactory thresholds. I also found a psych article that states that there are estrogen receptors found in some limbic system receptors that are terminals for olfactory neurons.

While I don't have the data to say you're wrong, I suspect that it's a more immediate effect on pre-existing receptors.

What an interesting study, though! Someone should totally do it - study the olfaction thresholds on women during their cycles, as well as during pregnancy and post-partum. The problem is that you'd need to actually biopsy the olfactory mucosa directly to prove in increased number of neurons, and no doctor will do that, as it can lead to direct anosmia. Perhaps a study that demonstrates changes in functional MRI perfusion following scent challenge during various levels of estrous? I should talk to some of my attendings about this.

JB

ann

I am not pregnant and I also crave certain smells. When the paper comes or I get a new book, I have to sniff it. When In walmart, I always walk through the tire section. Whats with that anyway?

Stacie

I am almost full term in my pregnancy with my second child and have been experiencing weird olfactory cravings. When I pass by a car service centre, or enter a parking garage I literally enter a state of euphoria! I am also craving the smell of liquid paper and permanent markers. I didn't experience any of this with my first pregnancy. All the articles Ive read associate olfactory cravings like this with PICA, but I haven't had any cravings to eat dirt yet, just to eat lots of meat, which I've been doing even though I've been a vegetarian for 15 years! I know I shouldn't be smelling the white out or the markers, and I do limit myself somewhat, but I CAN'T HELP MYSELF! Anyone else experience this?

Stacie

I am almost full term in my pregnancy with my second child and have been experiencing weird olfactory cravings. When I pass by a car service centre, or enter a parking garage I literally enter a state of euphoria! I am also craving the smell of liquid paper and permanent markers. I didn't experience any of this with my first pregnancy. All the articles Ive read associate olfactory cravings like this with PICA, but I haven't had any cravings to eat dirt yet, just to eat lots of meat, which I've been doing even though I've been a vegetarian for 15 years! I know I shouldn't be smelling the white out or the markers, and I do limit myself somewhat, but I CAN'T HELP MYSELF! Anyone else experience this?

Wendy

I can't believe this! I am not pregnant and I am having the same olfactory cravings as "Stacie".

I absloutely crave the smell of white out and gasoline from the gas station. I know how unhealthy these smells are (toxic-- actually).

I've spoken to my Internist about this and he's recommended that I see a Neurologist-- I hope it's not something serious. Everything I've found on the Internet is about loss of smell; not strange cravings!

Sariah

I am 34 weeks pregnant with my 4th child and I too crave the smell of toxic things. Spray paint, gasoline, nail polish, markers, etc. I also have to crunch on ice which I have always hated my whole life. And I too used to not eat meat but I just bought Wal-mart out of beef jerky and eat it all day long. I don't get it but I know my cravings are real. I feel for anyone out there that has weird attractions to all these crazy things. Let's just keep our sniffing to a minimum. Usually 2-3 sniffs a day is sufficient for me. :)

Sue

I can't bellieve this I am not crazy. I too crave the smell of gas. My mouth actually salavates like pavlow,s dog everytime I begin to pump at the gas station. I know it is PICA but I also read somewhere that it may be caused by an iron deficency. I am quite low on iron and have started a suppliment you guys may want to have some blood drawn to see if you too are animic.Good luck

Cristen

I also have these strange cravings I crave Ice all the time I swear I could practically go through a bag a day if i wanted, but I already know its because of my iron deficiency..also I thought this was very strange I get a craving for rubbing alcohol.. I am scared at times because I do not know if it effects the baby or not...if anyone has any idea please lemme know!!!

Julie

I have cravings for smelling gasoline, glue and other toxins and also like to crunch ice and have to have the flavor of wintermint alot. I eat altoids like peanuts. Brushing my teeth is also very gratifying and I tend to take longer brushing because of the flavor. I think this might be pre menapausal. Some of these symptoms were present when I was pregnant about 14 yrs ago.
Any possible ideas on what I can do to know more about these seemingly hormonal symptoms?

wendy

Cristen,

I have the same cravings as you and I am also pre-menapausal (I'm 46 years old). Most women experiencing the cravings for gas & other toxins seem to be pregnant-- you and I are 2 of the few that are done with our baby-making years.

I asked my gynocologist about it and he said he never heard of non-pregnant women reporting these symptoms. So I'm at a loss, as well.

Kelly

I am not usually a "posting" kind of person, but I googled olfactory cravings and found this site. I am almost 34 weeks pregnant, and for about 8 weeks now I CRAVE the smell of rubbing alcohol. My favorite is the wintergreen one. I just love it! I actually salivate at the thought. Never had this with first pregnancy or ever before. I had to look it up on the internet because I feel like I am absolutely nuts! So relieved I am not the only one.
k

cheryl anne

I am menopausal and crave lemons and limes- rinds and all????

Marya

I can't begin to tell you HOW MUCH IT MEANT TO ME to read your posts! I found your comments from having done a google search about my strange olfactory cravings (permanent markers, gasoline, moth balls, pine sol, rubber cement glue, nail polish remover, strong mints, etc!). I thought I was going crazy. My husband and friends think I'm a freak! Oh and I love to brush my teeth now all the time - and especially if I use "Tom's of Maine" brand (natural brand) spearmint toothpaste, cause it's less sweet. How weird. I brush it on my teeth and gums and will actually find myself fantasizing that it's one of those other products - how sick am ?! Thank goodness I read another woman's comments somewhere else about imagining she was eating HER obsession (laundry detergent) sprinkled all over her cereal (she pretends that's what she's eating, while she eats her cereal)! At least I know now that this might be more common than any of us are used to hearing/reading about - which is so relieving. My doctors have never heard of this. When I was pregnant with my son a few years ago I had it bad then, too. I googled and googled to no avail. I'm so, so glad to have found this forum! So my question is, are we certain that this is this just a form of PICA (not to make light of it), and does it simply mean I'm lacking iron? All these addictions/cravings/smells can be summed up as craving the sniffing of "organic solvents," and most of them contain either benzene or toluene, it appears, both of which are very dangerous for fetuses, if abused - particularly in the first trimester. It results primarily in babies born with birth defects similar to fetal alcohol symptom, both physically and mentally. Not trying to freak anyone out but that's what I've been reading tonight, online. The question is how much is truly dangerous (a little sniff here and there vs. really being bad...and hopefully none of us have been the latter). I've never been an "addictive personality" kind of person. I don't smoke, drink or do drugs - so this is so strange to me. The craving is unreal! Ok enough rambling...thanks everyone!

wendy

I've written in here before. I'm not pregnant yet I'm having strange olfactory cravings (permanent markers, gasoline, etc.)

I'm really worried that this is a symptom of some serious illness that we haven't identified-- not just a vitamin deficiency.

Has anyone out there been able to find a coorelation to these cravings and a disease?

Jim

I'm not pregnant nor do I have cravings, but in the last few days I have had an extremely heighted sense of smell. I'm goggling just to see if this is a symptom of something I might need to see a doctor about.

Betsy

I thought I was going crazy. I had surgery in May 2006, since then I have been having weird smell cravings. I crave the smell of charcoal(the pre-lit kind), exaust fumes and any petroleum smell. I asked my family doctor about it and he just laughed it off. I am really concerned about it. I have just turned 50 and am begining to start menopause. Please someone give me some advice.

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