The short answer is NO. First off, a single plus sign on your testing form represents the mildest of reactions; more of a potential sensitivity than a truly clinically significant allergy (especially if all your other fish and shellfish were negative across the board). Secondly, even if you did have major atopic complications due to fish or shellfish, those should not translate to fish OIL, since all allergens, by definition, are (molecular-structurally-speaking), proteinaceous. Fish oil’s name says it all, it is an OIL, which is a fat, not a protein. High quality fish oil products should and will be devoid of proteins. However, when you start bargain shopping and settle for those made under less stringent manufacturing regulations, you can end up with less pure, more contaminated capsules, which may contain not only some tiny modicum of fish protein, but also other fillers which may be allergenic or irritating.
Now for the longer answer: Even though you should be able to safely take high quality fish oil products, why would you?
The debate over omega 3’s and fish oil has been an exceedingly murky and highly contentious area in medicine for the past decade or so. In 1999, a famous study showed that patients taking omega 3’s were 10% less likely to get heart attacks, strokes, or die from cardiovascular disease, so for years PCP’s and cardiologists were putting everyone on them. However, since then, a myriad of studies has come out with varied and conflicting results. One of the most well known was in 2012 where the highly respected JAMA showed no reduction in MI, stroke or death. The problem with many articles is that they focused on patients with established CVS disease, who were often taking potential confounding prescriptions, and many used what critics stipulate were subtherapeutic doses of the study drug. Finally, in 2018, the “VITAL” study came out which looked at healthy subjects. They found that a gram of Lovaza was effective as a primary prevention for heart attacks – but not for stroke, cancer, or all causes of cardiovascular death. So, what are you to do with all this gobblygook data? Even the most recent critical review on the topic from March 2019 hedges a little in their recommendations, saying that better studies need to be done in order to confidently advise patients, but for now, given the fact that omega 3’s pose little risk and have few adverse effects, but great (or as some argue, proven) benefits, they won’t discourage their use in healthy subjects, and they (and the AHA) still advise certain high risk patients to continue supplementation.
The bottom line? The jury’s still out on if and how much fish oil is needed for cardiovascular health (and even further away from settling the debate over its use for inflammatory, neurologic, and psychiatric conditions), but since it probably won’t hurt, there’s no harm in trying it (other than to your wallet).
The one area everyone is in firm agreement on is that ensuring sufficient daily omega 3 intake, whether through diet and/or supplementation is essential in pregnancy.